01447nas a2200241 4500008004100000245005100041210005000092260004100142300001000183490000900193520076600202653001900968653002600987653001401013653001301027653002401040100002301064700002001087700002201107700001901129700002001148856003701168 2014 eng d00aDistributed OWL EL Reasoning: The Story So Far0 aDistributed OWL EL Reasoning The Story So Far aRiva del Garda, ItalybCEURc10/2014 a61-760 v12613 aAutomated generation of axioms from streaming data, such as traffic and text, can result in very large ontologies that single machine reasoners cannot handle. Reasoning with large ontologies requires distributed solutions. Scalable reasoning techniques for RDFS, OWL Horst and OWL 2 RL now exist. For OWL 2 EL, several distributed reasoning approaches have been tried, but are all perceived to be inefficient. We analyze this perception. We analyze completion rule based distributed approaches, using different characteristics, such as dependency among the rules, implementation optimizations, how axioms and rules are distributed. We also present a distributed queue approach for the classification of ontologies in description logic EL+(fragment of OWL 2 EL).10aclassification10adistributed reasoning10aMapReduce10aOWL 2 EL10apeer-to-peer system1 aMutharaju, Raghava1 aHitzler, Pascal1 aMateti, Prabhaker1 aLiebig, Thomas1 aFokoue, Achille uhttp://www.knoesis.org/node/222501315nas a2200181 4500008004100000245005700041210005700098260002100155520077100176653001900947653002600966653002700992100002301019700001801042700002001060700001601080856003701096 2013 eng d00aAutomatic Domain Identification for Linked Open Data0 aAutomatic Domain Identification for Linked Open Data aAtlanta, GAbACM3 aLinked Open Data (LOD) has emerged as one of the largest collections of interlinked structured datasets on the Web. Although the adoption of such datasets for applications is increasing, identifying relevant datasets for a specific task or topic is still challenging. As an initial step to make such identification easier, we provide an approach to automatically identify the topic domains of given datasets. Our method utilizes existing knowledge sources, more specifically Freebase, and we present an evaluation which validates the topic domains we can identify with our system. Furthermore, we evaluate the effectiveness of identified topic domains for the purpose of finding relevant datasets, thus showing that our approach improves reusability of LOD datasets.10aDataset search10aDomain Identification10aLinked Open Data Cloud1 aLalithsena, Sarasi1 aJain, Prateek1 aHitzler, Pascal1 aSheth, Amit uhttp://www.knoesis.org/node/227201154nas a2200133 4500008004100000245003600041210003600077260003300113520078400146100001600930700002000946700001700966856003700983 2013 eng d00aLogical Linked Data Compression0 aLogical Linked Data Compression aMontpellier, Francec05/20133 aLinked data has experienced accelerated growth in recent years. With the continuing proliferation of structured data, demand for RDF compression is becoming increasingly important. In this study, we introduce a novel lossless compression technique for RDF datasets, called Rule Based Compression (RB Compression) that compresses datasets by generating a set of new logical rules from the dataset and removing triples that can be inferred from these rules. Unlike other compression techniques, our approach not only takes advantage of syntactic verbosity and data redundancy but also utilizes semantic associations present in the RDF graph. Depending on the nature of the dataset, our system is able to prune more than 50% of the original triples without affecting data integrity.1 aJoshi, Amit1 aHitzler, Pascal1 aDong, Guozhu uhttp://www.knoesis.org/node/246101904nas a2200205 4500008004100000245004900041210004800090260002500138300001200163490000900175520134900184100001801533700001801551700002001569700001901589700001701608700001601625700002001641856003701661 2012 eng d00aAlignment-based Querying of Linked Open Data0 aAlignmentbased Querying of Linked Open Data aRome, Italyc09/2012 a807-8240 v75663 aThe Linked Open Data (LOD) cloud is rapidly becoming the largest interconnected source of structured data on diverse domains. The potential of the LOD cloud is enormous, ranging from solving challenging AI issues such as open domain question answering to automated knowledge discovery. However, due to an inherent distributed nature of LOD and a growing number of ontologies and vocabularies used in LOD datasets, querying over multiple datasets and retrieving LOD data remains a challenging task. In this paper, we propose a novel approach to querying linked data by using alignments for processing queries whose constituent data come from heterogeneous sources. We also report on our Alignment based Linked Open Data Querying System (ALOQUS) and present the architecture and associated methods. Using the state of the art alignment system BLOOMS, ALOQUS automatically maps concepts in users’ SPARQL queries, written in terms of a conceptual upper ontology or domain specific ontology, to different LOD concepts and datasets. It then creates a query plan, sends sub-queries to the different endpoints, crawls for co-referent URIs, merges the results and presents them to the user. We also compare the existing querying systems and demonstrate the added capabilities that the alignment based approach can provide for querying the Linked data.1 aKrishna, Amit1 aJain, Prateek1 aHitzler, Pascal1 aYeh, Peter, Z.1 aVerma, Kunal1 aSheth, Amit1 aDamova, Mariana uhttp://www.knoesis.org/node/278002071nas a2200397 4500008004100000245004300041210004300084260002600127300001000153520100000163653004001163100002101203700001701224700001501241700001901256700002001275700001401295700001801309700002401327700001601351700001901367700002001386700001501406700002201421700001601443700001901459700001801478700001901496700002001515700002401535700002101559700002001580700001601600700002001616856003701636 2012 eng d00aSemantics and Ontologies for EarthCube0 aSemantics and Ontologies for EarthCube aColumbus, OHc09/2012 a11-163 aSemantic technologies and ontologies play an increasing role in scientific workflow systems and knowledge infrastructures. While ontologies are mostly used for the semantic annotation of metadata, semantic technologies enable searching metadata catalogs beyond simple keywords, with some early evidence of semantics used for data translation. However, the next generation of distributed and interdisciplinary knowledge infrastructures will require capabilities beyond simple subsumption reasoning over subclass relations. In this work, we report from the EarthCube Semantics Community by highlighting which role semantics and ontologies should play in the EarthCube knowledge infrastructure. We target the interested domain scientist and, thus, introduce the value proposition of semantic technologies in a non-technical language. Finally, we commit ourselves to some guiding principles for the successful implementation and application of semantic technologies and ontologies within EarthCube.10aTractable Reasoning with Ontologies1 aBerg-Cross, Gary1 aCruz, Isabel1 aDean, Mike1 aFinin, Timothy1 aHitzler, Pascal1 aHua, Hook1 aGahegan, Mark1 aJanowicz, Krzysztof1 aLi, Naicong1 aMurphy, Philip1 aNordgren, Bryce1 aObrst, Leo1 aSchildhauer, Mark1 aSheth, Amit1 aSinha, Krishna1 aThessen, Anne1 aWiegand, Nancy1 aZaslavsky, Ilya1 aJanowicz, Krzysztof1 aKeßler, Carsten1 aKauppinen, Tomi1 aKolas, Dave1 aScheider, Simon uhttp://www.knoesis.org/node/268101271nas a2200217 4500008004100000245008200041210006900123260008800192520052900280653001200809653002200821653003100843653001000874653001700884653002600901100002100927700002100948700002700969700002000996856003701016 2011 eng d00aA Better Uncle For OWL - Nominal Schemas for Integrating Rules and Ontologies0 aBetter Uncle For OWL Nominal Schemas for Integrating Rules and O aNew YorkbProceedings of the 20th International World Wide Web Conference (WWW2011)3 aWe propose a description-logic style extension of OWL 2 with nominal schemas which can be used like 'variable nominal classes' within axioms. This feature allows ontology languages to express arbitrary DL-safe rules (as expressible in SWRL or RIF) in their native syntax. We show that adding nominal schemas to OWL 2 does not increase the worst-case reasoning complexity, and we identify a novel tractable language SROELV_3(⊓, X) that is versatile enough to capture the lightweight languages OWL EL and OWL RL.10aDatalog10aDescription Logic10aSemantic Web Rule Language10aSROIQ10atractability10aWeb Ontology Language1 aKrotzsch, Markus1 aMaier, Frederick1 aKrisnadhi, Adila, Alfa1 aHitzler, Pascal uhttp://www.knoesis.org/node/109102040nas a2200121 4500008004100000245007000041210006900111520165400180100001201834700001501846700002001861856003701881 2011 eng d00aComputing Inconsistency Measure based on Paraconsistent Semantics0 aComputing Inconsistency Measure based on Paraconsistent Semantic3 aMeasuring inconsistency in knowledge bases has been recognized as an important problem in several research areas. Many methods have been proposed to solve this problem and a main class of them is based on some kind of paraconsistent semantics. However, existing methods suffer from two limitations: (i) they are mostly restricted to propositional knowledge bases; (ii) very few of them discuss computational aspects of computing inconsistency measures. In this article, we try to solve these two limitations by exploring algorithms for computing an inconsistency measure of first-order knowledge bases. After introducing a four-valued semantics for first-order logic, we define an inconsistency measure of a first-order knowledge base, which is a sequence of inconsistency degrees. We then propose a precise algorithm to compute our inconsistency measure. We show that this algorithm reduces the computation of the inconsistency measure to classical satisfiability checking. This is done by introducing a new semantics, named S[n]-4 semantics, which can be calculated by invoking a classical SAT solver. Moreover, we show that this auxiliary semantics also gives a direct way to compute upper and lower bounds of inconsistency degrees. That is, it can be easily revised to compute approximating inconsistency measures. The approximating inconsistency measures converge to the precise values if enough resources are available. Finally, by some nice properties of the S[n]-4 semantics, we show that some upper and lower bounds can be computed in P-time, which says that the problem of computing these approximating inconsistency measures is tractable.1 aMa, Yue1 aQi, Guilin1 aHitzler, Pascal uhttp://www.knoesis.org/node/159802076nas a2200229 4500008004100000245009000041210006900131260007500200520130400275653003401579653002101613653002101634653002101655100001801676700001901694700001701713700002301730700002001753700002001773700001601793856003701809 2011 eng d00aContextual Ontology Alignment of LOD With an Upper Ontology: A Case Study With Proton0 aContextual Ontology Alignment of LOD With an Upper Ontology A Ca aGreecebProceedings of 8th Extended Semantic Web Conference, ESWC 20113 aThe Linked Open Data (LOD) is a major milestone towards realizing the Semantic Web vision, and can enable applications such as robust Question Answering (QA) systems that can answer queries requiring multiple, disparate information sources. However, realizing these applications requires relationships at both the schema and instance level, but currently the LOD only provides relationships for the latter. To address this limitation, we present a solution for automatically finding schema-level links between two LOD ontologies -- in the sense of ontology alignment. Our solution, called BLOOMS+, extends our previous solution (i.e. BLOOMS) in two significant ways. BLOOMS+ 1) uses a more sophisticated metric to determine which classes between two ontologies to align, and 2) considers contextual information to further support (or reject) an alignment. We present a comprehensive evaluation of our solution using schema-level mappings from LOD ontologies to Proton (an upper level ontology) -- created manually by human experts for a real world application called FactForge. We show that our solution performed well on this task. We also show that our solution significantly outperformed existing ontology alignment solutions (including our previously published work on BLOOMS) on this same task.10aContextual Ontology Alignment10aLinked Open Data10aOntology Mapping10aSchema Alignment1 aJain, Prateek1 aYeh, Peter, Z.1 aVerma, Kunal1 aVasquez, Reymonrod1 aDamova, Mariana1 aHitzler, Pascal1 aSheth, Amit uhttp://www.knoesis.org/node/108201204nas a2200133 4500008004100000245006700041210006600108260011200174520068000286100002000966700002700986700002001013856003701033 2011 eng d00aLocal Closed World Reasoning: Grounded Circumscription for OWL0 aLocal Closed World Reasoning Grounded Circumscription for OWL aBonn, GermanybProceedings, Part I. Lecture Notes in Computer Science Vol. 7031, Springer, Heidelberg, 20113 aWe present a new approach to adding closed world reasoning to the Web Ontology Language OWL. It transcends previous work on circumscriptive description logics which had the drawback of yielding an undecidable logic unless severe restrictions were imposed. In particular, it was not possible, in general, to apply local closure to roles. In this paper, we provide a new approach, called grounded circumscrip- tion, which is applicable to SROIQ and other description logics around OWL without these restrictions. We show that the resulting language is decidable, and we derive an upper complexity bound. We also provide a decision procedure in the form of a tableaux algorithm.1 aSengupta, Kunal1 aKrisnadhi, Adila, Alfa1 aHitzler, Pascal uhttp://www.knoesis.org/node/120301066nas a2200169 4500008004100000245008200041210006900123260009300192520044200285653002000727653002200747653002300769100002000792700002700812700002000839856003700859 2011 eng d00aLocal closed world semantics: grounded circumscription for description logics0 aLocal closed world semantics grounded circumscription for descri aGalway, IrelandbLecture Notes in Computer Science Vol. 6902, Springer, Heidelberg, 20113 aWe present an improved local closed world extension for description logics. It is based on circumscription, and deviates from previous circumscriptive description logics [1,3] in that extensions of minimized predicates may contain only extensions of named individuals in the knowledge base. Besides an (arguably) higher intuitive appeal, the improved semantics is applicable to expressive description logics without loss of decidability.10acircumscription10aDescription Logic10alocal closed world1 aSengupta, Kunal1 aKrisnadhi, Adila, Alfa1 aHitzler, Pascal uhttp://www.knoesis.org/node/117700492nas a2200157 4500008004100000245005800041210005500099653002000154653001700174653001700191653002200208100002700230700002000257700002000277856003700297 2011 eng d00aLocal Closed World Semantics: Keep it simple, stupid!0 aLocal Closed World Semantics Keep it simple stupid10acircumscription10aclosed world10adecidability10aDescription Logic1 aKrisnadhi, Adila, Alfa1 aSengupta, Kunal1 aHitzler, Pascal uhttp://www.knoesis.org/node/230901554nas a2200181 4500008004100000245009000041210006900131520093600200653003801136653002901174653002201203653002801225653001701253100002001270700002501290700002001315856003701335 2011 eng d00aLocal Closed-World Reasoning with Description Logics under the Well-founded Semantics0 aLocal ClosedWorld Reasoning with Description Logics under the We3 aAn important question for the upcoming Semantic Web is how to best combine open world ontology languages, such as the OWL-based ones, with closed world rule-based languages. One of the most mature proposals for this combination is known as hybrid MKNF knowledge bases (Motik and Rosati, 2010 [52]), and it is based on an adaptation of the Stable Model Semantics to knowledge bases consisting of ontology axioms and rules. In this paper we propose a well-founded semantics for nondisjunctive hybrid MKNF knowledge bases that promises to provide better efficiency of reasoning, and that is compatible with both the OWL-based semantics and the traditional Well-Founded Semantics for logic programs. Moreover, our proposal allows for the detection of inconsistencies, possibly occurring in tightly integrated ontology axioms and rules, with only little additional effort. We also identify tractable fragments of the resulting language.10aDescription logics and ontologies10aKnowledge Representation10alogic programming10aNon-monotonic reasoning10aSemantic Web1 aKnorr, Matthias1 aAlferes, Jose, Julio1 aHitzler, Pascal uhttp://www.knoesis.org/node/159700848nas a2200133 4500008004100000245006500041210006500106520041700171100002100588700002100609700002700630700002000657856003700677 2011 eng d00aNominal Schemas for Integrating Rules and Description Logics0 aNominal Schemas for Integrating Rules and Description Logics3 aWe propose an extension of SROIQ with nominal schemas which can be used like Âvariable nominal conceptsÂ within axioms. This feature allows us to express arbitrary DL-safe rules in description logic syntax. We show that adding nominal schemas to SROIQ does not increase its worst-case reasoning complexity, and we identify a family of tractable DLs SROELVn that allow for restricted use of nominal schemas.1 aKrotzsch, Markus1 aMaier, Frederick1 aKrisnadhi, Adila, Alfa1 aHitzler, Pascal uhttp://www.knoesis.org/node/183600925nas a2200133 4500008004100000245001800041210001800059260013600077520047300213100002700686700002100713700002000734856003700754 2011 eng d00aOWL and Rules0 aOWL and Rules bReasoning Web. Semantic Technologies for the Web of Data. 7th International Summer School 2011, Galway, Ireland, August 23-27, 20113 aThe relationship between the Web Ontology Language OWL and rule-based formalisms has been the subject of many discussions and research investigations, some of them controversial. From the many attempts to reconcile the two paradigms, we present some of the newest developments. More precisely, we show which kind of rules can be modeled in the current version of OWL, and we show how OWL can be extended to incorporate rules without compromising OWL design principles.1 aKrisnadhi, Adila, Alfa1 aMaier, Frederick1 aHitzler, Pascal uhttp://www.knoesis.org/node/195301461nas a2200133 4500008004100000245006100041210006100102260010600163520096700269100001801236700001601254700002001270856003701290 2011 eng d00aParaconsistent Semantics for Hybrid MKNF Knowledge Bases0 aParaconsistent Semantics for Hybrid MKNF Knowledge Bases aGalway, IrelandbProceedings. Lecture Notes in Computer Science Vol. 6902, Springer, Heidelberg, 20113 aHybrid MKNF knowledge bases, originally based on the stable model semantics, is a mature method of combining rules and Description Logics (DLs). The well-founded semantics for such knowledge bases has been proposed subsequently for better efficiency of reasoning. However, integration of rules and DLs may give rise to inconsistencies, even if they are respectively consistent. Accordingly, reasoning systems based on the previous two semantics will break down. In this paper, we employ the four-valued logic proposed by Belnap, and present a paraconsistent semantics for Hybrid MKNF knowledge bases, which can detect inconsistencies and handle it effectively. Besides, we transform our proposed semantics to the stable model semantics via a linear transformation operator, which indicates that the data complexity in our paradigm is not higher than that of classical reasoning. Moreover, we provide a fixpoint algorithm for computing paraconsistent MKNF models.1 aHuang, Shasha1 aLi, Qingguo1 aHitzler, Pascal uhttp://www.knoesis.org/node/117900997nas a2200157 4500008004100000245003000041210003000071520046900101653011600570100002800686700002700714700002100741700002000762700002000782856003700802 2011 eng d00aReconciling OWL and Rules0 aReconciling OWL and Rules3 aWe report on a recent advance in integrating Rules and OWL. We discuss a recent proposal, known as nominal schemas, which realizes a seamless integration of Datalog rules into the description logic SROIQ which underlies OWL 2 DL. We present extensions of the standardized OWL syntaxes to incorporate nominal schemas, reasoning algorithms, and a rst naive implementation. And we argue why this approach goes a long way towards overcoming the present paradigm split.10aOWL and description logic and decidability and local closed world and reasoningalgorithms and rules and datalog1 aMartinez, David, Carral1 aKrisnadhi, Adila, Alfa1 aMaier, Frederick1 aSengupta, Kunal1 aHitzler, Pascal uhttp://www.knoesis.org/node/194901385nas a2200157 4500008004100000245006100041210006000102260003000162520084800192653006501040100001701105700003201122700001601154700002001170856003701190 2011 eng d00aRepresentation of Parsimonious Covering Theory in OWL-DL0 aRepresentation of Parsimonious Covering Theory in OWLDL aSan Francisco, California3 aThe Web Ontology Language has not been designed for representing abductive inference, which is often required for applications such as medical disease diagnosis. As a consequence, existing OWL ontologies have limited ability to encode knowledge for such applications. In the last 150 years, many logic frameworks for the representation of abductive inference have been developed. Among these frameworks, Parsimonious Covering Theory (PCT) has achieved wide recognition. PCT is a formal model of diagnostic reasoning in which knowledge is represented as a network of causal associations, and whose goal is to account for observed symptoms with plausible explanatory hypotheses. In this paper, we argue that OWL does provide some of the expressivity required to approximate diagnostic reasoning, and outline a suitable encoding of PCT in OWL-DL.10aOWL and Abductive Reasoning and Parsimonious Covering Theory1 aHenson, Cory1 aThirunarayan, Krishnaprasad1 aSheth, Amit1 aHitzler, Pascal uhttp://www.knoesis.org/node/166700327nas a2200109 4500008004100000245004300041210004200084300001000126100002400136700002000160856003700180 2011 eng d00aSemantic Web surveys and applications.0 aSemantic Web surveys and applications a65-661 aJanowicz, Krzysztof1 aHitzler, Pascal uhttp://www.knoesis.org/node/240200687nas a2200133 4500008004100000245003600041210003500077260001400112300000800126520033800134100002000472700002400492856003700516 2011 eng d00aSemantic Web Tools and Systems.0 aSemantic Web Tools and Systems bIOS Press a1-23 aSemantic Web research relies on a number of key methodologies such as knowledge representation languages or reasoning algorithms. As a research community, however, we could not progress based on these methodologies exclusively, but require tools and systems that realize our research results as key technologies for the Semantic Web.1 aHitzler, Pascal1 aJanowicz, Krzysztof uhttp://www.knoesis.org/node/240301372nas a2200109 4500008004100000245008000041210006900121260016600190520084900356100002001205856003701225 2011 eng d00aWhat's happening in Semantic Web ... and what FCA could have to do with it.0 aWhats happening in Semantic Web and what FCA could have to do wi aFormal Concept Analysis, 9th International Conference, ICFCA 2011, Nicosia, Cyprus, May 2011bLecture Notes in Artificial Intelligence 6628, Springer, Heidelberg3 aThe Semantic Web [27] is gaining momentum. Driven by over 10 years of focused project funding in the US and the EU, Semantic Web Technologies are now entering application areas in industry, academia, government, and the open Web. The Semantic Web is based on the idea of describing the meaning - or semantics - of data on the Web using metadata - data that describes other data - in the form of ontologies, which are represented using logic-based knowledge representation languages [26]. Central to the transfer of Semantic Web into practice is the Linked Open Data effort [7], which has already resulted in the publication, on the Web, of billions of pieces of information using ontology languages. This provides the basic data needed for establishing intelligent system applications on the Web in the tradition of Semantic Web Technologies.
1 aHitzler, Pascal uhttp://www.knoesis.org/node/117600332nas a2200085 4500008004100000245007900041210006900120100002000189856003700209 2011 eng d00aWhat's happening in Semantic Web ... and what FCA could have to do with it0 aWhats happening in Semantic Web and what FCA could have to do wi1 aHitzler, Pascal uhttp://www.knoesis.org/node/233501368nas a2200133 4500008004100000245004900041210004900090260001800139520097400157100002701131700001901158700002001177856003701197 2010 eng d00aApproximate Instance Retrieval on Ontologies0 aApproximate Instance Retrieval on Ontologies aBilbao, Spain3 aWith the development of more expressive description logics(DLs) for the Web Ontology Language OWL the question arises how we can properly deal with the high computational complexity for efficient reasoning. In application cases that require scalable reasoning with expressive ontologies, non-standard reasoning solutions such as approximate reasoning are necessary to tackle the intractability of reasoning in expressive DLs. In this paper, we are concerned with the approximation of the reasoning task of instance retrieval on DL knowledge bases, trading correctness of retrieval results for gain of speed. We introduce our notion of an approximate concept extension and we provide implementations to compute an approximate answer for a concept query by a suitable mapping to efficient database operations. Furthermore, we report on experiments of our approach on instance retrieval with the Wine ontology and discuss first results in terms of error rate and speed-up.1 aTserendorj, Tuvshintur1 aGrimm, Stephan1 aHitzler, Pascal uhttp://www.knoesis.org/node/124501495nas a2200205 4500008004100000245008100041210006900122300000900191520087500200653001401075653002901089653003001118653002301148100001201171700001501183700001701198700002001215700001701235856003701252 2010 eng d00aComputational Complexity and Anytime Algorithm for Inconsistency Measurement0 aComputational Complexity and Anytime Algorithm for Inconsistency a3-213 aMeasuring inconsistency degrees of inconsistent knowledge bases is an important problem as it provides context information for facilitating inconsistency handling. Many methods have been proposed to solve this problem and a main class of them is based on some kind of paraconsistent semantics. In this paper, we consider the computational aspects of inconsistency degrees of propositional knowledge bases under 4-valued semantics. We first give a complete analysis of the computational complexity of computing inconsistency degrees. As it turns out that computing the exact inconsistency degree is intractable, we then propose an anytime algorithm that provides tractable approximations of the inconsistency degree from above and below. We show that our algorithm satisfies some desirable properties and give experimental results of our implementation of the algorithm. 10aalgorithm10acomputational complexity10ainconsistency measurement10amulti-valued logic1 aMa, Yue1 aQi, Guilin1 aXiao, Guohui1 aHitzler, Pascal1 aLin, Zuoquan uhttp://www.knoesis.org/node/161801741nas a2200181 4500008004100000245007000041210006900111300001200180520116300192653002301355653003201378653002501410653001701435653003201452100001801484700002001502856003701522 2010 eng d00aConcept Learning in Description Logics Using Refinement Operators0 aConcept Learning in Description Logics Using Refinement Operator a203-2503 aWith the advent of the Semantic Web, description logics have become one of the most prominent paradigms for knowledge representation and reasoning. Progress in research and applications, however, is constrained by the lack of well-structured knowledge bases consisting of a sophisticated schema and instance data adhering to this schema. It is paramount that suitable automated methods for their acquisition, maintenance, and evolution will be developed. In this paper, we provide a learning algorithm based on refinement operators for the description logic ALCQ including support for concrete roles. We develop the algorithm from thorough theoretical foundations by identifying possible abstract property combinations which refinement operators for description logics can have. Using these investigations as a basis, we derive a practically useful complete and proper refinement operator. The operator is then cast into a learning algorithm and evaluated using our implementation DL-Learner. The results of the evaluation show that our approach is superior to other learning approaches on description logics, and is competitive with established ILP systems.10adescription logics10aInductive logic programming10aRefinement operators10aSemantic Web10aStructured machine learning1 aLehmann, Jens1 aHitzler, Pascal uhttp://www.knoesis.org/node/162800665nas a2200205 4500008004100000245009000041210006900131260003200200300001000232490000900242653004200251100001800293700001500311700001700326700002300343700002000366700002000386700001600406856003700422 2010 eng d00aContextual Ontology Alignment of LOD with an Upper Ontology: A Case Study with Proton0 aContextual Ontology Alignment of LOD with an Upper Ontology A Ca aHeraklion, GreecebSpringer a80-920 v664310aontology alignment and lod and proton1 aJain, Prateek1 aYeh, Peter1 aVerma, Kunal1 aVasquez, Reymonrod1 aDamova, Mariana1 aHitzler, Pascal1 aSheth, Amit uhttp://www.knoesis.org/node/190501434nas a2200121 4500008004100000245008400041210006900125260008100194520096800275100001201243700002001255856003701275 2010 eng d00aDistance-based Measures of Inconsistency and Incoherency for Description Logics0 aDistancebased Measures of Inconsistency and Incoherency for Desc aWaterloo, Canadab23rd International Workshop on Description Logics (DL2010)3 aInconsistency and incoherency are two sorts of erroneous information in a DL ontology which have been widely discussed in ontology-based applications. For example, they have been used to detect modeling errors during ontology construction. To provide more informative metrics which can tell the differences between inconsistent ontologies and between incoherent terminologies, there has been some work on measuring inconsistency of an ontology and on measuring incoherency of a terminology. However, most of them merely focus either on measuring inconsistency or on measuring incoherency and no clear ideas of how to extend them to allow for the other. In this paper, we propose a novel approach to measure DL ontologies, named distance-based measures. It has the merits that both inconsistency and incoherency can be measured in a unified framework. Moreover, only classical DL interpretations are used such that there is no restriction on the DL languages used.1 aMa, Yue1 aHitzler, Pascal uhttp://www.knoesis.org/node/184601322nas a2200145 4500008004100000245007000041210006900111520084200180653003101022653002701053100001801080700002101098700002001119856003701139 2010 eng d00aExtracting Reduced Logic Programs from Artificial Neural Networks0 aExtracting Reduced Logic Programs from Artificial Neural Network3 aArtificial neural networks can be trained to perform excellently in many application areas. While they can learn from raw data to solve sophisticated recognition and analysis problems, the acquired knowledge remains hidden within the network architecture and is not readily accessible for analysis or further use: Trained networks are *black boxes*. Recent research efforts therefore investigate the possibility to extract symbolic knowledge from trained networks, in order to analyze, validate, and reuse the structural insights gained implicitly during the training process. In this paper, we will study how knowledge in form of propositional logic programs can be obtained in such a way that the programs are as *simple* as possible - where *simple* is being understood in some clearly defined and meaningful way.10aartificial neural networks10areduced logic programs1 aLehmann, Jens1 aBader, Sebastian1 aHitzler, Pascal uhttp://www.knoesis.org/node/162001212nas a2200145 4500008004100000245005200041210005100093260014800144520059500292653008800887100001800975700002000993700001601013856003701029 2010 eng d00aFlexible Bootstrapping-Based Ontology Alignment0 aFlexible BootstrappingBased Ontology Alignment bThe Fifth International Workshop on Ontology Matching collocated with the 9th International Semantic Web Conference ISWC-2010, November 7, 20103 aBLOOMS (Jain et al, ISWC2010) is an ontology alignment system which, in its core, utilizes the Wikipedia category hierarchy for establishing alignments. In this paper, we present a Plug-and-Play extension to BLOOMS, which allows to flexibly replace or complement the use of Wikipedia by other online or offline resources, including domain-specific ontologies or taxonomies. By making use of automated translation services and of Wikipedia in languages other than English, it makes it possible to apply BLOOMS to alignment tasks where the input ontologies are written in different languages.10aOntology Matching and Wikipedia and BLOOMS and Plug-n-Play Ontology Matching System1 aJain, Prateek1 aHitzler, Pascal1 aSheth, Amit uhttp://www.knoesis.org/node/188700443nam a2200133 4500008004100000245004500041210004500086653003200131653004500163100002000208700002100228700002300249856003700272 2010 eng d00aFoundations of Semantic Web Technologies0 aFoundations of Semantic Web Technologies10afoundations of semantic web10afoundations of semantic web technologies1 aHitzler, Pascal1 aKrotzsch, Markus1 aRudolph, Sebastian uhttp://www.knoesis.org/node/210401326nas a2200205 4500008004100000245006400041210006400105300001200169520071800181653002700899653002500926653002200951653001700973653002000990653001301010653001801023100002201041700002001063856003701083 2010 eng d00aGeneralized Distance Functions in the Theory of Computation0 aGeneralized Distance Functions in the Theory of Computation a443-4643 aWe discuss a number of distance functions encountered in the theory of computation, including metrics, ultra-metrics, quasi-metrics, generalized ultrametrics, partial metrics, d-ultra-metrics, and generalized metrics. We consider their properties, associated fixed-point theorems, and some general applications they have within the theory of computation. We consider in detail the applications of generalized distance functions in giving a uniform treatment of several important semantics for logic programs, including acceptable programs and natural generalizations of them, and also the supported model and the stable model in the context of locally stratified extended disjunctive logic programs and databases.10adenotational semantics10afixed-point theorems10alogic programming10astable model10asupported model10atopology10aultra-metrics1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/161901519nas a2200241 4500008004100000245004300041210004300084260003000127520083500157653002100992653002401013653001701037653001501054653002601069653002801095653002701123100001801150700002001168700001601188700001901204700001701223856003701240 2010 eng d00aHow To Make Linked Data More than Data0 aHow To Make Linked Data More than Data aSan Francisco, California3 aThe LOD cloud has a potential for applicability in many AI-related tasks, such as open domain question answering, knowledge discovery, and the Semantic Web. An important prerequisite before the LOD cloud can enable these goals is allowing its users (and applications) to effectively pose queries to and retrieve answers from it. However, this prerequisite is still an open problem for the LOD cloud and has restricted it to 'merely more data.' To transform the LOD cloud from 'merely more data' to 'semantically linked data' there are plenty of open issues which should be addressed. We believe this transformation of the LOD cloud can be performed by addressing the shortcomings identified by us: lack of conceptual description of datasets, lack of expressivity, and difficulties with respect to querying.10aLinked Open Data10aLod federated query10aLoD ontology10aLoD Schema10aLoD Schema Entichment10aLoD Semantic Enrichment10aSPARQL federated query1 aJain, Prateek1 aHitzler, Pascal1 aSheth, Amit1 aYeh, Peter, Z.1 aVerma, Kunal uhttp://www.knoesis.org/node/212901252nas a2200145 4500008004100000245004700041210004700088260004000135520081400175100002000989700002001009700002001029700002001049856003701069 2010 eng d00aLearning Paradigms in Dynamic Environments0 aLearning Paradigms in Dynamic Environments aDagstuhl, GermanybSchloss Dagstuhl3 aThe seminar centered around problems which arise in the context of machine learning in dynamic environments. Particular emphasis was put on a couple of specific questions in this context: how to represent and abstract knowledge appropriately to shape the problem of learning in a partially unknown and complex environment and how to combine statistical inference and abstract symbolic representations; how to infer from few data and how to deal with non i.i.d. data, model revision and life-long learning; how to come up with efficient strategies to control realistic environments for which exploration is costly, the dimensionality is high and data are sparse; how to deal with very large settings; and how to apply these models in challenging application areas such as robotics, computer vision, or the web.1 aHammer, Barbara1 aHitzler, Pascal1 aMaass, Wolfgang1 aToussaint, Marc uhttp://www.knoesis.org/node/185401034nas a2200229 4500008004100000020002200041245003600063210003600099260003900135300001000174520041600184653002800600653001600628653001700644653001600661100001800677700002000695700001900715700001700734700001600751856003700767 2010 eng d a978-1-57735-461-100aLinked Data is Merely More Data0 aLinked Data is Merely More Data aMenlo Park, CaliforniabAAAI Press a82-863 aIn this position paper, we argue that the Linked Open Data (LoD) Cloud, in its current form, is only of limited value for furthering the Semantic Web vision. Being merely a weakly linked 'triple collection', it will only be of very limited benefit for the AI or Semantic Web communities. We describe the corresponding problems with the LoD Cloud and give directions for research to remedy the situation.10aArtificial Intelligence10aLinked Data10aSemantic Web10aWeb of Data1 aJain, Prateek1 aHitzler, Pascal1 aYeh, Peter, Z.1 aVerma, Kunal1 aSheth, Amit uhttp://www.knoesis.org/node/104601016nas a2200133 4500008004100000245003400041210003100075260002100106520065400127100002300781700002100804700002000825856003700845 2010 eng d00aA MapReduce Algorithm for EL+0 aMapReduce Algorithm for EL aWaterloo, Canada3 aRecently, the use of the MapReduce framework for distributed RDF Schema reasoning has shown that it is possible to compute the deductive closure of sets of over a billion RDF triples within a reasonable time span [22], and that it is also possible to carry the approach over to OWL Horst [21]. Following this lead, in this paper we provide a MapReduce algorithm for the description logic EL+, more precisely for the classification of EL+ ontologies. To do this, we first modify the algorithm usually used for EL+ classification. The modified algorithm can then be converted into a MapReduce algorithm along the same key ideas as used for RDF schema.1 aMutharaju, Raghava1 aMaier, Frederick1 aHitzler, Pascal uhttp://www.knoesis.org/node/184700330nam a2200097 4500008004100000245005600041210005600097100002200153700002000175856003700195 2010 eng d00aMathematical Aspects of Logic Programming Semantics0 aMathematical Aspects of Logic Programming Semantics1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/209700795nas a2200133 4500008004100000245005800041210005700099520028200156653011800438100002100556700002700577700002000604856003700624 2010 eng d00aNominal Schemas for Integrating Rules and Ontologies.0 aNominal Schemas for Integrating Rules and Ontologies3 aWe propose a description-logic style extension of OWL DL, which includes DL-safe variable SWRL and seamlessly integrates datalog rules. Our language also sports a tractable fragment, which we call ELP 2, covering OWL EL, OWL RL, most of OWL QL, and variable restricted datalog.10aWeb Ontology Language and Description Logic and SROIQ and Semantic Web Rule Language and Datalog and tractability1 aMaier, Frederick1 aKrisnadhi, Adila, Alfa1 aHitzler, Pascal uhttp://www.knoesis.org/node/195701629nas a2200229 4500008004100000245004400041210004400085260002000129520099600149653001101145653002101156653003701177653002301214653002101237653001401258100001801272700002001290700001601310700001701326700001901343856003701362 2010 eng d00aOntology Alignment for Linked Open Data0 aOntology Alignment for Linked Open Data aShanghai, China3 aThe Web of Data currently coming into existence through the Linked Open Data (LOD) effort is a major milestone in realizing the Semantic Web vision. However, the development of applications based on LOD faces difficulties due to the fact that the different LOD datasets are rather loosely connected pieces of information. In particular, links between LOD datasets are almost exclusively on the level of instances, and schema-level information is being ignored. In this paper, we therefore present a system for finding schema-level links between LOD datasets in the sense of ontology alignment. Our system, called BLOOMS, is based on the idea of bootstrapping information already present on the LOD cloud. We also present a comprehensive evaluation which shows that BLOOMS outperforms state-of-the-art ontology alignment systems on LOD datasets. At the same time, BLOOMS is also competitive compared with these other systems on the Ontology Evaluation Alignment Initiative Benchmark datasets.10aBLOOMS10aLinked Open Data10aLinked Open Data Schema Matching10aontology alignment10aSchema Alignment10aWikipedia1 aJain, Prateek1 aHitzler, Pascal1 aSheth, Amit1 aVerma, Kunal1 aYeh, Peter, Z. uhttp://www.knoesis.org/node/127801538nas a2200157 4500008004100000245007000041210006900111300001200180520103700192653003901229100001601268700002001284700002001304700001901324856003701343 2010 eng d00aPerspectives and Challenges for Recurrent Neural Network Training0 aPerspectives and Challenges for Recurrent Neural Network Trainin a617-6193 aRecurrent neural networks (RNNs) offer flexible machine learning tools which share the learning abilities of feedforward networks and which extend their expression abilities based on dynamical equations. Hence, they can directly process complex spatiotemporal data and model complex dynamic systems. Since temporal and spatial data are present in many domains such as processing environmental time series, modelling the financial market, speech and language processing, robotics, bioinformatics, medical informatics, etc., RNNs constitute promising candidates for a variety of applications. Further, their rich dynamic repertoire as time dependent systems makes them suitable candidates for modelling brain phenomena or mimicking large-scale distributed computations and argumentations. Thus, RNNs carry the promise of efficient biologically plausible signal processing models optimally suited for a wide area of industrial applications on the one hand and an explanation of cognitive phenomena of the human brain on the other hand.10aneural network training challenges1 aGori, Marco1 aHammer, Barbara1 aHitzler, Pascal1 aPalm, Guenther uhttp://www.knoesis.org/node/161702147nas a2200193 4500008004100000245009100041210006900132260002400201300001200225490000900237520143300246653012701679100001701806700002501823700003201848700002001880700001601900856003701916 2010 eng d00aProvenance Context Entity (PaCE): Scalable Provenance Tracking for Scientific RDF Data0 aProvenance Context Entity PaCE Scalable Provenance Tracking for aHeidelberg, Germany a461-4700 v61873 aThe Resource Description Framework (RDF) format is being used by a large number of scientific applications to store and disseminate their datasets. The provenance information, describing the source or lineage of the datasets, is playing an increasingly significant role in ensuring data quality, computing trust value of the datasets, and ranking query results. Current provenance tracking approaches using the RDF reification vocabulary suffer from a number of known issues, including lack of formal semantics, use of blank nodes, and application-dependent interpretation of reified RDF triples. In this paper, we introduce a new approach called Provenance Context Entity (PaCE) that uses the notion of provenance context to create provenance-aware RDF triples. We also define the formal semantics of PaCE through a simple extension of the existing RDF(S) semantics that ensures compatibility of PaCE with existing Semantic Web tools and implementations. We have implemented the PaCE approach in the Biomedical Knowledge Repository (BKR) project at the US National Library of Medicine. The evaluations demonstrate a minimum of 49% reduction in total number of provenance-specific RDF triples generated using the PaCE approach as compared to RDF reification. In addition, performance for complex queries improves by three orders of magnitude and remains comparable to the RDF reification approach for simpler provenance queries.10aProvenir ontology and Provenance context entity and Biomedical knowledge repository and Context theory and RDF reification1 aSahoo, Satya1 aBodenreider, Olivier1 aThirunarayan, Krishnaprasad1 aHitzler, Pascal1 aSheth, Amit uhttp://www.knoesis.org/node/190602477nas a2200301 4500008004100000245009100041210006900132260010100201520143300302653003601735653001901771653003101790653003001821653000901851653000901860653002301869653003001892653003601922653002201958653002001980653002402000100002102024700003202045700002502077700002002102700001602122856003702138 2010 eng d00aProvenance Context Entity (PaCE): Scalable Provenance Tracking for Scientific RDF Data0 aProvenance Context Entity PaCE Scalable Provenance Tracking for bThe 22nd International Conference on Scientific and Statistical Database Management (SSDBM) 20103 aThe Resource Description Framework (RDF) format is being used by a large number of scientific applications to store and disseminate their datasets. The provenance information, describing the source or lineage of the datasets, is playing an increasingly significant role in ensuring data quality, computing trust value of the datasets, and ranking query results. Current provenance tracking approaches using the RDF reification vocabulary suffer from a number of known issues, including lack of formal semantics, use of blank nodes, and application-dependent interpretation of reified RDF triples. In this paper, we introduce a new approach called Provenance Context Entity (PaCE) that uses the notion of provenance context to create provenance-aware RDF triples. We also define the formal semantics of PaCE through a simple extension of the existing RDF(S) semantics that ensures compatibility of PaCE with existing Semantic Web tools and implementations. We have implemented the PaCE approach in the Biomedical Knowledge Repository (BKR) project at the US National Library of Medicine. The evaluations demonstrate a minimum of 49% reduction in total number of provenance-specific RDF triples generated using the PaCE approach as compared to RDF reification. In addition, performance for complex queries improves by three orders of magnitude and remains comparable to the RDF reification approach for simpler provenance queries.10aBiomedical knowledge repository10aContext theory10adomain specific provenance10aModel theoretic semantics10aPACE10aPrOM10aProvenance context10aProvenance context entity10aProvenance Management Framework10aProvenir ontology10aRDF reification10asemantic provenance1 aSahoo, Satya, S.1 aThirunarayan, Krishnaprasad1 aBodenreider, Olivier1 aHitzler, Pascal1 aSheth, Amit uhttp://www.knoesis.org/node/106001490nas a2200181 4500008004100000245003000041210002800071260001400099300001000113520101000123653002401133653002101157653002801178653002101206100002401227700002001251856003701271 2010 eng d00aA Reasonable Semantic Web0 aReasonable Semantic Web bIOS Press a39-443 aThe realization of Semantic Web reasoning is central to substantiating the Semantic Web vision. However, current mainstream research on this topic faces serious challenges, which forces us to question established lines of research and to rethink the underlying approaches. We argue that reasoning for the Semantic Web should be understood as 'shared inference,' which is not necessarily based on deductive methods. Model-theoretic semantics (and sound and complete reasoning based on it) functions as a gold standard, but applications dealing with large-scale and noisy data usually cannot afford the required runtimes. Approximate methods, including deductive ones, but also approaches based on entirely different methods like machine learning or natureinspired computing need to be investigated, while quality assurance needs to be done in terms of precision and recall values (as in information retrieval) and not necessarily in terms of soundness and completeness of the underlying algorithms.10aAutomated Reasoning10aFormal Semantics10aKnowledgeRepresentation10aLinked Open Data1 aVan Harmelen, Frank1 aHitzler, Pascal uhttp://www.knoesis.org/node/155601809nas a2200193 4500008004100000245006200041210005800103260002300161300000800184490000600192520126600198653001801464653002101482653001701503653001401520100002001534700002401554856003701578 2010 eng d00aSemantic Web - Interoperability, Usability, Applicability0 aSemantic Web Interoperability Usability Applicability bIOS Pressc01/2010 a1-20 v13 aWhile this statement seems obvious, this has not been so a few years ago, when basic research funding seemed to be running out, and industrial uptake was hardly happening. In the meantime, we do not only see sustained funding for Semantic Web related research (in particular by the European Commission), but also significant investment by industry, including major IT and venture capital companies. The Semantic Web is here to stay – and to grow. The Semantic Web is multidisciplinary and heterogeneous. Many Semantic Web researchers maintain close ties to neighboring disciplines which provide methods or application areas for their work. However, the Semantic Web has now established itself as a research field in its own rights. Consequently, a growing number of researchers, in particular those of the second or third generation, seem to identify themselves with the Semantic Web as their primary field of work. The growing number of top quality events dedicated to Semantic Web topics is also a clear indication of this trend. Another indicator is the increasing interweavement of Semantic Web methods into related disciplines leading to research topics such as geospatialsemantics, the Semantic Sensor Web, semantic desktop, or work on cultural heritage10aApplicability10aInteroperability10aSemantic Web10aUsability1 aHitzler, Pascal1 aJanowicz, Krzysztof uhttp://www.knoesis.org/node/155501249nas a2200145 4500008004100000245006500041210006200106520081700168100001200985700001500997700001701012700001701029700002001046856003701066 2009 eng d00aAn Anytime Algorithm for Computing Inconsistency Measurement0 aAnytime Algorithm for Computing Inconsistency Measurement3 aMeasuring inconsistency degrees of inconsistent knowledge bases is an important problem as it provides context information for facilitating inconsistency handling. Many methods have been proposed to solve this problem and a main class of them is based on some kind of paraconsistent semantics. In this paper, we consider the computational aspects of inconsistency degrees of propositional knowledge bases under 4-valued semantics. We first analyze its computational complexity. As it turns out that computing the exact inconsistency degree is intractable, we then propose an anytime algorithm that provides tractable approximation of the inconsistency degree from above and below.We show that our algorithm satisfies some desirable properties and give experimental results of our implementation of the algorithm.1 aMa, Yue1 aQi, Guilin1 aXiao, Guohui1 aLin, Zuoquan1 aHitzler, Pascal uhttp://www.knoesis.org/node/124600540nas a2200145 4500008004100000245007300041210006900114260006800183100002300251700001800274700002300292700002200315700002000337856003700357 2009 eng d00aAn Evolutionary Computing Approach for Reasoning in the Semantic Web0 aEvolutionary Computing Approach for Reasoning in the Semantic We bInternational Workshop on Collective Intelligence and Evolution1 aRudolph, Sebastian1 aTagni, Gaston1 aGueret, Christophe1 aSchlobach, Stefan1 aHitzler, Pascal uhttp://www.knoesis.org/node/178900790nas a2200121 4500008004100000245004600041210004600087300001000133520044400143100002400587700002000611856003700631 2009 eng d00aFacets of Artificial General Intelligence0 aFacets of Artificial General Intelligence a58-593 aWe argue that time has come for a serious endeavor to work towards artificial general intelligence (AGI). This positive assessment of the very possibility of AGI has partially its roots in the development of new methodological achievements in the AI area, like new learning paradigms and new integration techniques for different methodologies. The article sketches some of these methods as prototypical examples for approaches towards AGI.1 aKuhnberger, Kai-Uwe1 aHitzler, Pascal uhttp://www.knoesis.org/node/162300342nam a2200109 4500008004100000245004500041210004500086100002300131700002100154700002000175856003700195 2009 eng d00aFoundations of Semantic Web Technologies0 aFoundations of Semantic Web Technologies1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/209800678nas a2200133 4500008004100000245002500041210002500066520034400091653000800435653002600443100001800469700002000487856003700507 2009 eng d00aOntologies and Rules0 aOntologies and Rules3 aThe Web Ontology Language OWL, as introduced in Chapter 4, is the language recommended by the World Wide Web consortium (W3C) for expressing ontologies for the Semantic Web. OWL is based on Description Logics, see Chapter 1, and as such is based on first-order predicate logic as underlying knowledge representation and reasoning paradigm.10aOWL10aWeb Ontology Language1 aParsia, Bijan1 aHitzler, Pascal uhttp://www.knoesis.org/node/205601255nas a2200133 4500008004100000245003900041210003900080260010500119300001200224520081600236100001201052700002001064856003701084 2009 eng d00aParaconsistent Reasoning for OWL 20 aParaconsistent Reasoning for OWL 2 aChantilly, VA, USAbWeb Reasoning and Rule Systems, Third International Conference, RR 2009c10/2009 a197-2113 aA four-valued description logic has been proposed to reason with description logic based inconsistent knowledge bases. This approach has a distinct advantage that it can be implemented by invoking classical reasoners to keep the same complexity as under the classical semantics. However, this approach has so far only been studied for the basid description logic ALC. In this paper, we further study how to extend the four-valued semantics to the more expressive description logic SROIQ which underlies the forthcoming revision of the Web Ontology Language, OWL 2, and also investigate how it fares when adapated to tractable description logics including EL++, DL-Lite, and Horn-DLs. We define the four-valued semantics along the same lines as for ALC and show that we can retain most of the desired properties.1 aMa, Yue1 aHitzler, Pascal uhttp://www.knoesis.org/node/125001346nas a2200133 4500008004100000245006200041210006000103260006700163300001000230520089600240100001901136700002001155856003701175 2009 eng d00aA Preferential Tableaux Calculus for Circumscriptive ALCO0 aPreferential Tableaux Calculus for Circumscriptive ALCO aChantilly, VA, USAbInternational Conference, RR 2009c10/2009 a40-543 aNonmonotonic extensions of description logics (DLs) allow for default and local closed-world reasoning and are an acknowledged desired feature for applications, e.g. in the Semantic Web. A recent approach to such an extension is based on McCarthy's circumscription, which rests on the principle of minimising the extension of selected predicates to close off dedicated parts of a domain model. While decidability and complexity results have been established in the literature, no practical algorithmisation for circumscriptive DLs has been proposed so far. In this paper, we present a tableaux calculus that can be used as a decision procedure for concept satisfiability with respect to concept circumscribed ALCO knowledge bases. The calculus builds on existing tableaux for classical DLs, extended by the notion of a preference clash to detect the non-minimality of constructed models.1 aGrimm, Stephan1 aHitzler, Pascal uhttp://www.knoesis.org/node/124401830nas a2200145 4500008004100000245007200041210006900113520135900182100001601541700002001557700003201577700002101609700001701630856003701647 2009 eng d00aPrOM: A Semantic Web Framework for Provenance Management in Science0 aPrOM A Semantic Web Framework for Provenance Management in Scien3 aThe eScience paradigm is enabling researchers to collaborate over the Web in virtual laboratories and conduct experiments on an industrial scale. But, the inherent variability in the quality and trust associated with eScience resources necessitates the use of provenance information describing the origin of an entity. Existing systems often model provenance using ambiguous terminology, have poor domain semantics and include modeling inconsistencies that hinders interoperability. Further, mere collection of provenance information is of little value without a well-defined and scalable query mechanism. In this paper, we present 'PrOM', a framework that addresses both the modeling and querying issues in eScience provenance management. The theoretical underpinning for PrOM consists of, (a) a novel foundational ontology for provenance representation called 'Provenir', and (b) the first set of query operators to be defined for provenance query and analysis. The PrOM framework also includes a scalable provenance query engine that supports complex queries (high 'expression complexity') over a very large real world dataset with 308 million RDF triples. The query engine uses a new class of materialized views for query optimization that confers significant advantages (up to three orders of magnitude) in query performance.1 aSheth, Amit1 aHitzler, Pascal1 aThirunarayan, Krishnaprasad1 aSahoo, Satya, S.1 aBarga, Roger uhttp://www.knoesis.org/node/194000699nas a2200109 4500008004100000245002600041210002600067260007900093520036000172100002000532856003700552 2009 eng d00aSuggestions for OWL 30 aSuggestions for OWL 3 b5th International Workshop on OWL: Experiences and Directions (OWLED 2009)3 aWith OWL 2 about to be completed, it is the right time to start discussions on possible future modifications of OWL. We present here a number of suggestions in order to discuss them with the OWL user community. They encompass expressive extensions on polynomial OWL 2 profiles, a suggestion for an OWL Rules language, and expressive extensions for OWL DL.1 aHitzler, Pascal uhttp://www.knoesis.org/node/184800583nas a2200109 4500008004100000245003300041210003300074260003300107520027600140100002000416856003700436 2009 eng d00aTowards Reasoning Pragmatics0 aTowards Reasoning Pragmatics aMexico City, Mexicoc12/20093 aThe realization of Semantic Web reasoning is central to substantiating the Semantic Web vision. However, current mainstream research on this topic faces serious challenges, which force us to question established lines of research and to rethink the underlying approaches.1 aHitzler, Pascal uhttp://www.knoesis.org/node/124701352nas a2200133 4500008004100000245005200041210005200093520094500145100002301090700002101113700002701134700002001161856003701181 2008 eng d00aApproximate OWL Instance Retrieval with Screech0 aApproximate OWL Instance Retrieval with Screech3 aWith the increasing interest in expressive ontologies for the Semantic Web, it is critical to develop scalable and efficient ontology reasoning techniques that can properly cope with very high data volumes. For certain application domains, approximate reasoning solutions, which trade soundness or completeness for increased reasoning speed, will help to deal with the high computational complexities which state of the art ontology reasoning tools have to face. In this paper, we present a comprehensive overview of the SCREECH approach to approximate instance retrieval with OWL ontologies, which is based on the KAON2 algorithms, facilitating a compilation of OWL DL TBoxes into Datalog, which is tractable in terms of data complexity. We present three different instantiations of the Screech approach, and report on experiments which show that the gain in efficiency outweighs the number of introduced mistakes in the reasoning process.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aTserendorj, Tuvshintur1 aHitzler, Pascal uhttp://www.knoesis.org/node/118201271nas a2200157 4500008004100000245004300041210004200084260007400126300001200200520077300212100002300985700002101008700002701029700002001056856003701076 2008 eng d00aApproximate OWL-Reasoning with Screech0 aApproximate OWLReasoning with Screech aKarlsruhe, GermanybSecond International Conference, RR 2008c10/2008 a165-1803 aApplications of expressive ontology reasoning for the Semantic Web require scalable algorithms for deducing implicit knowledge from explicitly given knowledge bases. Besides the development of more efficient such algorithms, awareness is rising that approximate reasoning solutions will be helpful and needed for certain application domains. In this paper, we present a comprehensive overview of the Screech approach to approximate reasoning with OWL ontologies, which is based on the KAON2 algorithms, facilitating a compilation of OWL DL TBoxes into Datalog, which is tractable in terms of data complexity.We present three different instantiations of the Screech approach, and report on experiments which show that a significant gain in efficiency can be achieved.
1 aRudolph, Sebastian1 aKrotzsch, Markus1 aTserendorj, Tuvshintur1 aHitzler, Pascal uhttp://www.knoesis.org/node/125101111nas a2200145 4500008004100000245005900041210005900100260003000159300001200189520066300201100002300864700002100887700002000908856003700928 2008 eng d00aCheap Boolean Role Constructors for Description Logics0 aCheap Boolean Role Constructors for Description Logics aDresden, Germanyc09/2008 a362-3743 aWe investigate the possibility of incorporating Boolean role constructors on simple roles into some of today's most popular description logics, focussing on cases where those extensions do not increase complexity of reasoning. We show that the expressive DLs SHOIQ and SROIQ, serving as the logical underpinning of OWL and the forthcoming OWL 2, can accommodate arbitrary Boolean expressions. The prominent OWL-fragment SHIQ can be safely extended by safe role expressions, and the tractable fragments EL++ and DLP retain tractability if extended by conjunction on roles, where in the case of DLP the restriction on role simplicity can even be discarded.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/125501300nas a2200145 4500008004100000245006600041210006300107260009200170300001100262520077900273100002001052700002501072700002001097856003701117 2008 eng d00aA Coherent Well-founded Model for Hybrid MKNF Knowledge Bases0 aCoherent Wellfounded Model for Hybrid MKNF Knowledge Bases aPatras, Greeceb18th European Conference on Artificial Intelligence, ECAI 2008c07/2008 a99-1033 aWith the advent of the Semantic Web, the question becomes important how to best combine open-world based ontology languages, like OWL, with closed-world rules paradigms. One of the most mature proposals for this combination is known as Hybrid MKNF knowledge bases [11], which is based on an adaptation of the stable model semantics to knowledge bases consisting of ontology axioms and rules. In this paper, we propose a well-founded semantics for such knowledge bases which promises to provide better efficiency of reasoning, which is compatible both with the OWL-based semantics and the traditional well-founded semantics for logic programs, and which surpasses previous proposals for such a well-founded semantics by avoiding some issues related to inconsistency handling.1 aKnorr, Matthias1 aAlferes, Jose, Julio1 aHitzler, Pascal uhttp://www.knoesis.org/node/125601524nas a2200181 4500008004100000245005900041210005700100300001400157520094400171653003501115653003101150653003201181653002701213100002101240700002401261700002001285856003701305 2008 eng d00aConnectionist Model Generation: A First-Order Approach0 aConnectionist Model Generation A FirstOrder Approach a2420-24323 aKnowledge based artificial neural networks have been applied quite successfully to propositional knowledge representation and reasoning tasks. However, as soon as these tasks are extended to structured objects and structure-sensitive processes as expressed e.g., by means of first-order predicate logic, it is not obvious at all what neural symbolic systems would look like such that they are truly connectionist, are able to learn, and allow for a declarative reading and logical reasoning at the same time. The core method aims at such an integration. It is a method for connectionist model generation using recurrent networks with feed-forward core.We show in this paper how the core method can be used to learn first-order logic programs in a connectionist fashion, such that the trained network is able to do reasoning over the acquired knowledge. We also report on experimental evaluations which show the feasibility of our approach.10aConnectionist Model Generation10aFirst-Order Logic Programs10aNeural-Symbolic Integration10aRecurrent RBF Networks1 aBader, Sebastian1 aHolldobler, Steffen1 aHitzler, Pascal uhttp://www.knoesis.org/node/162201094nas a2200121 4500008004100000245006100041210006100102260004900163520068400212100001900896700002000915856003700935 2008 eng d00aDefeasible Inference with Circumscriptive OWL Ontologies0 aDefeasible Inference with Circumscriptive OWL Ontologies b5th European Semantic Web Conference, ESWC083 aThe Web Ontology Language (OWL) adheres to the openworld assumption and can thus not be used for forms of nonmonotonic reasoning or defeasible inference, an acknowledged desirable feature in open Semantic Web environments. We investigate the use of the formalism of circumscriptive description logics (DLs) to realise defeasible inference within the OWL framework. By example, we demonstrate how reasoning with (restricted) circumscribed OWL ontologies facilitates various forms of defeasible inference, also in comparison to alternative approaches. Moreover, we sketch an extension to DL tableaux for handling the circumscriptive case and report on a preliminary implementation.1 aGrimm, Stephan1 aHitzler, Pascal uhttp://www.knoesis.org/node/185001083nas a2200145 4500008004100000245009400041210006900135260009600204300001200300520052400312100002300836700002100859700002000880856003700900 2008 eng d00aDescription Logic Reasoning with Decision Diagrams: Compiling SHIQ to Disjunctive Datalog0 aDescription Logic Reasoning with Decision Diagrams Compiling SHI aKarlsruhe, GermanybThe Semantic Web - ISWC 2008, 7th International Semantic Web Conference a435-4503 aWe propose a novel method for reasoning in the description logic SHIQ. After a satisfiability preserving transformation from SHIQ to the description logic ALCIb, the obtained ALCIb Tbox T is converted into an ordered binary decision diagram (OBDD) which represents a canonical model for T. This OBDD is turned into a disjunctive datalog program that can be used for Abox reasoning. The algorithm is worst-case optimal w.r.t. data complexity, and admits easy extensions with DL-safe rules and ground conjunctive queries.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/124801218nas a2200145 4500008004100000245002800041210002800069260002800097300001000125520083600135100002300971700002100994700002001015856003701035 2008 eng d00aDescription Logic Rules0 aDescription Logic Rules aPatras, Greecec07/2008 a80-843 aWe introduce description logic (DL) rules as a new rule-based formalism for knowledge representation in DLs. As a fragment of the Semantic Web Rule Language SWRL, DL rules allow for a tight integration with DL knowledge bases. In contrast to SWRL, however, the combination of DL rules with expressive description logics remains decidable, and we show that the DL SROIQ - the basis for the ongoing standardisation of OWL 2 - can completely internalise DL rules. On the other hand, DL rules capture many expressive features of SROIQ that are not available in simpler DLs yet. While reasoning in SROIQ is highly intractable, it turns out that DL rules can be introduced to various lightweight DLs without increasing their worst-case complexity. In particular, DL rules enable us to significantly extend the tractable DLs EL++ and DLP.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/125701159nas a2200121 4500008004100000245003500041210003400076520082600110100002100936700002300957700002000980856003701000 2008 eng d00aELP: Tractable Rules for OWL 20 aELP Tractable Rules for OWL 23 aWe introduce ELP as a decidable fragment of the Semantic Web Rule Language (SWRL) that admits reasoning in polynomial time. ELP is based on the tractable description logic EL++, and encompasses an extended notion of the recently proposed DL rules for that logic. Thus ELP extends EL++ with a number of features introduced by the forthcoming OWL 2, such as disjoint roles, local reflexivity, certain range restrictions, and the universal role.We present a reasoning algorithm based on a translation of ELP to Datalog, and this translation also enables the seamless integration of DL-safe rules into ELP.While reasoning with DL-safe rules as such is already highly intractable, we show that DL-safe rules based on the Description Logic Programming (DLP) fragment of OWL 2 can be admitted in ELP without losing tractability.1 aKrotzsch, Markus1 aRudolph, Sebastian1 aHitzler, Pascal uhttp://www.knoesis.org/node/125301161nas a2200121 4500008004100000245003500041210003400076520082800110100002300938700002100961700002000982856003701002 2008 eng d00aELP: Tractable Rules for OWL 20 aELP Tractable Rules for OWL 23 aWe introduce ELP as a decidable fragment of the Semantic Web Rule Language (SWRL) that admits reasoning in polynomial time. ELP is based on the tractable description logic EL++, and encompasses an extended notion of the recently proposed DL rules for that logic. Thus ELP extends EL++ with a number of features introduced by the forthcoming OWL 2, such as disjoint roles, local reflexivity, certain range restrictions, and the universal role. We present a reasoning algorithm based on a translation of ELP to Datalog, and this translation also enables the seamless integration of DL-safe rules into ELP. While reasoning with DL-safe rules as such is already highly intractable, we show that DL-safe rules based on the Description Logic Programming (DLP) fragment of OWL 2 can be admitted in ELP without losing tractability.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/125201159nas a2200121 4500008004100000245003500041210003400076520082600110100002100936700002300957700002000980856003701000 2008 eng d00aELP: Tractable Rules for OWL 20 aELP Tractable Rules for OWL 23 aWe introduce ELP as a decidable fragment of the Semantic Web Rule Language (SWRL) that admits reasoning in polynomial time. ELP is based on the tractable description logic EL++, and encompasses an extended notion of the recently proposed DL rules for that logic. Thus ELP extends EL++ with a number of features introduced by the forthcoming OWL 2, such as disjoint roles, local reflexivity, certain range restrictions, and the universal role.We present a reasoning algorithm based on a translation of ELP to Datalog, and this translation also enables the seamless integration of DL-safe rules into ELP.While reasoning with DL-safe rules as such is already highly intractable, we show that DL-safe rules based on the Description Logic Programming (DLP) fragment of OWL 2 can be admitted in ELP without losing tractability.1 aKrotzsch, Markus1 aRudolph, Sebastian1 aHitzler, Pascal uhttp://www.knoesis.org/node/193501230nas a2200121 4500008004100000245006500041210006500106520083600171100002301007700002101030700002001051856003701071 2008 eng d00aExpressive Tractable Description Logics based on SROIQ Rules0 aExpressive Tractable Description Logics based on SROIQ Rules3 aWe introduce description logic (DL) rules as a new rule-based formalism for knowledge representation in DLs. As a fragment of the Semantic Web Rule Language SWRL, DL rules allow for a tight integration with DL knowledge bases. In contrast to SWRL, however, the combination of DL rules with expressive description logics remains decidable, and we show that the DL SROIQ - the basis for the ongoing standardisation of OWL 2 - can completely internalise DL rules. On the other hand, DL rules capture many expressive features of SROIQ that are not available in simpler DLs yet. While reasoning in SROIQ is highly intractable, it turns out that DL rules can be introduced to various lightweight DLs without increasing their worst-case complexity. In particular, DL rules enable us to significantly extend the tractable DLs EL++ and DLP.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/193301005nas a2200145 4500008004100000245008500041210006900126260004900195520051000244100001500754700001600769700001700785700002000802856003700822 2008 eng d00aA Forgetting-based Approach for Handling Inconsistency in Distributed Ontologies0 aForgettingbased Approach for Handling Inconsistency in Distribut b5th European Semantic Web Conference, ESWC083 aIn the context of multiple distributed ontologies, we are often confronted with the problem of dealing with inconsistency. In this paper, we propose an approach for reasoning with inconsistent distributed ontologies based on *concept forgetting*.We firstly define *concept forgetting* in description logics.We then adapt the notions of recoveries and preferred recoveries in propositional logic to description logics. Two consequence relations are then defined based on the preferred recoveries.1 aQi, Guilin1 aWang, Yimin1 aHaase, Peter1 aHitzler, Pascal uhttp://www.knoesis.org/node/185200315nas a2200109 4500008004100000245003500041210003500076100002000111700001700131700002000148856003700168 2008 eng d00aLearning Expressive Ontologies0 aLearning Expressive Ontologies1 aVolker, Johanna1 aHaase, Peter1 aHitzler, Pascal uhttp://www.knoesis.org/node/205301294nas a2200133 4500008004100000245007700041210006900118260006200187520082500249100001201074700001701086700002001103856003701123 2008 eng d00aParaconsistent Reasoning for Expressive and Tractable Description Logics0 aParaconsistent Reasoning for Expressive and Tractable Descriptio b21st International Workshop on Description Logics, DL20083 aFour-valued description logic has been proposed to reason with description logic based inconsistent knowledge bases, mainly ALC. This approach has a distinct advantage that it can be implemented by invoking classical reasoners to keep the same complexity as classical semantics. In this paper, we further study how to extend the four-valued semantics to more expressive description logics, such as SHIQ, and to more tractable description logics including EL++, DL-Lite, and Horn-DLs. The most effort we spend defining the four-valued semantics of expressive four-valued description logics is on keeping the reduction from four-valued semantics to classical semantics as in the case of ALC; While for tractable description logics, we mainly focus on how to maintain their tractability when adopting four-valued semantics.1 aMa, Yue1 aLin, Zuoquan1 aHitzler, Pascal uhttp://www.knoesis.org/node/184901227nas a2200109 4500008004100000245003800041210003800079520092400117100001901041700002001060856003701080 2008 eng d00aReasoning in Circumscriptive ALCO0 aReasoning in Circumscriptive ALCO3 aNon-monotonic extensions of description logics (DLs) allow for default and local closed-world reasoning and are an acknowledged desired feature for applications, e.g. in the Semantic Web. A recent approach to such an extension is based on McCarthy's circumscription, which rests on the principle of minimising the extension of selected predicates to locally close off dedicated parts of a domain model. While decidability and complexity results have been established in the literature, no practical algorithmisation for circumscriptive DLs has been proposed so far. In this paper, we present a tableaux calculus that can be used as a sound and complete decision procedure for concept satisfiability with respect to concept-circumscribed ALCO knowledge bases. The calculus builds on existing tableaux for classical DLs, extended by the notion of a preference clash to detect the non-minimality of constructed models.1 aGrimm, Stephan1 aHitzler, Pascal uhttp://www.knoesis.org/node/193401447nas a2200145 4500008004100000245007600041210006900117300001100186520096800197653002701165653003301192100001901225700002001244856003701264 2008 eng d00aSemantic Matchmaking of Web Resources with Local Closed-World Reasoning0 aSemantic Matchmaking of Web Resources with Local ClosedWorld Rea a89-1263 aOntology languages like OWL allow for semantically rich annotation of resources, such as products advertised at an electronic online marketplace,while the Description Logic (DL) formalism underlying OWL provides reasoning techniques to perform matchmaking on such annotations. We identify peculiarities in the use of DL inferences for matchmaking which are due to the open-world semantics of OWL, and we analyse the use of local closed-world reasoning for its applicability to matchmaking. In particular,we investigate two nonmonotonic extensions to DL, namely auto epistemic DLs and DLs with circumscription, for their suitability of realising local closed-world reasoning in the matchmaking context to overcome these problems. We discuss their different characteristics by means of an elab- orate example of an electronic marketplace for PC product catalogues from the eCommerce domain and demonstrate how these formalisms can be used to realise such scenarios.10aclosed-world reasoning10alocal closed world reasoning1 aGrimm, Stephan1 aHitzler, Pascal uhttp://www.knoesis.org/node/162100336nam a2200121 4500008004100000245002900041210002800070100002300098700001500121700002100136700002000157856003700177 2008 eng d00aSemantic Web. Grundlagen0 aSemantic Web Grundlagen1 aRudolph, Sebastian1 aSure, York1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/210500379nas a2200145 4500008004100000022002200041245001700063210001700080300001200097100002000109700002000129700002600149700002100175856003700196 2008 eng d a978-3-87005-073-300aSpieltheorie0 aSpieltheorie a117-1251 aHitzler, Pascal1 aHitzler, Pascal1 aChocholaty, Alexander1 aKalmbach, Gudrun uhttp://www.knoesis.org/node/205200895nas a2200121 4500008004100000245007500041210006900116520048700185100002300672700002100695700002000716856003700736 2008 eng d00aTerminological Reasoning in SHIQ with Ordered Binary Decision Diagrams0 aTerminological Reasoning in SHIQ with Ordered Binary Decision Di3 aWe present a new algorithm for reasoning in the description logic SHIQ, which is the most prominent fragment of the Web Ontology Language OWL. The algorithm is based on ordered binary decision diagrams (OBDDs) as a data structure for storing and operating on large model representations. We thus draw on the success and the proven scalability of OBDD-based systems. To the best of our knowledge, we present the very first algorithm for using OBDDs for reasoning with general Tboxes.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/125400895nas a2200121 4500008004100000245007500041210006900116520048700185100002300672700002100695700002000716856003700736 2008 eng d00aTerminological Reasoning in SHIQ with Ordered Binary Decision Diagrams0 aTerminological Reasoning in SHIQ with Ordered Binary Decision Di3 aWe present a new algorithm for reasoning in the description logic SHIQ, which is the most prominent fragment of the Web Ontology Language OWL. The algorithm is based on ordered binary decision diagrams (OBDDs) as a data structure for storing and operating on large model representations. We thus draw on the success and the proven scalability of OBDD-based systems. To the best of our knowledge, we present the very first algorithm for using OBDDs for reasoning with general Tboxes.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/193201299nas a2200133 4500008004100000245005600041210005600097260002300153520089100176100002001067700002101087700002001108856003701128 2007 eng d00aAcquisition of OWL DL Axioms from Lexical Resources0 aAcquisition of OWL DL Axioms from Lexical Resources aInnsbruck, Austria3 aState-of-the-art research on automated learning of ontologies from text currently focuses on inexpressive ontologies. The acquisition of complex axioms involving logical connectives, role restrictions, and other expressive features of the Web Ontology Language OWL remains largely unexplored. In this paper, we present a method and implementation for enriching inexpressive OWL ontologies with expressive axioms which is based on a deep syntactic analysis of natural language definitions. We argue that it can serve as a core for a semi-automatic ontology engineering process supported by a methodology that integrates methods for both ontology learning and evaluation. The feasibility of our approach is demonstrated by generating complex class descriptions from Wikipedia definitions and from a fishery glossary provided by the Food and Agriculture Organization of the United Nations.1 aVolker, Johanna1 aCimiano, Philipp1 aHitzler, Pascal uhttp://www.knoesis.org/node/121901106nas a2200157 4500008004100000245008500041210006900126260002100195300001100216520062000227100001200847700001500859700001700874700002000891856003700911 2007 eng d00aAn Algorithm for Computing Inconsistency Measurement by Paraconsistent Semantics0 aAlgorithm for Computing Inconsistency Measurement by Paraconsist aHammamet,Tunisia a91-1023 aMeasuring inconsistency in knowledge bases has been recognized as an important problem in many research areas. Most of approaches proposed for measuring inconsistency are based on paraconsistent semantics. However, very few of them provide an algorithm for implementation. In this paper, we first give a four-valued semantics for first-order logic and then propose an approach for measuring the degree of inconsistency based on this four-valued semantics. After that, we propose an algorithm to compute the inconsistency degree by introducing a new semantics for first order logic, which is called S[n]-4 semantics.1 aMa, Yue1 aQi, Guilin1 aLin, Zuoquan1 aHitzler, Pascal uhttp://www.knoesis.org/node/121500378nas a2200121 4500008004100000245005300041210005300094260002300147100001200170700001700182700002000199856003700219 2007 eng d00aAlgorithms for Paraconsistent Reasoning with OWL0 aAlgorithms for Paraconsistent Reasoning with OWL aInnsbruck, Austria1 aMa, Yue1 aLin, Zuoquan1 aHitzler, Pascal uhttp://www.knoesis.org/node/122101108nas a2200133 4500008004100000245004000041210003900081260011900120300001000239520064800249100002000897700002000917856003700937 2007 eng d00aAny-World Access to OWL from Prolog0 aAnyWorld Access to OWL from Prolog aKI, Osnabruck, GermanybAdvances in Artificial Intelligence, 30th Annual German Conference on AI, KI 2007c09/2007 a84-983 aThe W3C standard OWL provides a decidable language for representing ontologies. While its use is rapidly spreading, efforts are being made by researchers worldwide to augment OWL with additional expressive features or by interlacing it with other forms of knowledge representation, in order to make it applicable for even further purposes. In this paper, we integrate OWL with one of the most successful and most widely used forms of knowledge representation, namely Prolog, and present a hybrid approach which layers Prolog on top of OWL in such a way that the open-world semantics of OWL becomes directly accessible within the Prolog system.1 aMatzner, Tobias1 aHitzler, Pascal uhttp://www.knoesis.org/node/126401414nas a2200121 4500008004100000245005500041210005200096260005400148520101300202100002001215700002001235856003701255 2007 eng d00aA Comparison of Disjunctive Well-founded Semantics0 aComparison of Disjunctive Wellfounded Semantics bFoundations of Artificial Intelligence (FAInt-07)3 aWhile the stable model semantics, in the form of Answer Set Programming, has become a successful semantics for disjunctive logic programs, a corresponding satisfactory extension of the well-founded semantics to disjunctive programs remains to be found. The many current proposals for such an extension are so diverse, that even a systematic comparison between them is a challenging task. In order to aid the quest for suitable disjunctive well-founded semantics, we present a systematic approach to a comparison based on level mappings, a recently introduced framework for characterizing logic programming semantics, which was quite successfully used for comparing the major semantics for normal logic programs. We extend this framework to disjunctive logic programs, which will allow us to gain comparative insights into their different handling of negation. Additionally, we show some of the problems occurring when trying to handle minimal models (and thus disjunctive stable models) within the framework.1 aKnorr, Matthias1 aHitzler, Pascal uhttp://www.knoesis.org/node/185301108nas a2200133 4500008004100000245005400041210005400095260004000149520068400189100002300873700002100896700002000917856003700937 2007 eng d00aComplexity Boundaries for Horn Description Logics0 aComplexity Boundaries for Horn Description Logics aVancouver, British Columbia, Canada3 aHorn description logics (Horn-DLs) have recently started to attract attention due to the fact that their (worst-case) data complexities are in general lower than their overall (i.e. combined) complexities, which makes them attractive for reasoning with large ABoxes. However, the natural question whether Horn-DLs also provide advantages for TBox reasoning has hardly been addressed so far. In this paper, we therefore provide a thorough and comprehensive analysis of the combined complexities of Horn-DLs. While the combined complexity for many Horn-DLs turns out to be the same as for their non-Horn counterparts, we identify subboolean DLs where Hornness simplifies reasoning.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/121701032nas a2200121 4500008004100000245004200041210004200083520068400125100002300809700002100832700002000853856003700873 2007 eng d00aComplexity of Horn Description Logics0 aComplexity of Horn Description Logics3 aHorn description logics (Horn-DLs) have recently started to attract attention due to the fact that their (worst-case) data complexities are in general lower than their overall (i.e. combined) complexities, which makes them attractive for reasoning with large ABoxes. However, the natural question whether Horn-DLs also provide advantages for TBox reasoning has hardly been addressed so far. In this paper, we therefore provide a thorough and comprehensive analysis of the combined complexities of Horn-DLs. While the combined complexity for many Horn-DLs turns out to be the same as for their non-Horn counterparts, we identify subboolean DLs where Hornness simplifies reasoning.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/193101129nas a2200145 4500008004100000245006000041210005900101260014000160300001200300520057000312100002300882700002100905700002000926856003700946 2007 eng d00aConjunctive Queries for a Tractable Fragment of OWL 1.10 aConjunctive Queries for a Tractable Fragment of OWL 11 aBusan, KoreabThe Semantic Web, 6th International Semantic Web Conference, 2nd Asian Semantic Web Conference, ISWC 2007 + ASWCc11/2007 a310-3233 aDespite the success of the Web Ontology Language OWL, the development of expressive means for querying OWL knowledge bases is still an open issue. In this paper, we investigate how a very natural and desirable form of queries-namely conjunctive ones-can be used in conjunction with OWL such that one of the major design criteria of the latter-namely decidability-can be retained. More precisely, we show that querying the tractable fragment EL++ of OWL 1.1 is decidable. We also provide a complexity analysis and show that querying unrestricted EL++ is undecidable.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/126201528nas a2200145 4500008004100000245008300041210006900124520103900193653002801232100002101260700002401281700002001305700002001325856003701345 2007 eng d00aThe Core Method: Connectionist Model Generation for First-Order Logic Programs0 aCore Method Connectionist Model Generation for FirstOrder Logic 3 aIn Artificial Intelligence, knowledge representation studies the formalisation of knowledge and its processing within machines. Techniques of automated reasoning allow a computer system to draw conclusions from knowledge represented in a machine-interpretable form. Recently, ontologies have evolved in computer science as computational artefacts to provide computer systems with a conceptual yet computational model of a particular domain of interest. In this way, computer systems can base decisions on reasoning about domain knowledge, similar to humans. This chapter gives an overview on basic knowledge representation aspects and on ontologies as used within computer systems. After introducing ontologies in terms of their appearance, usage and classification, it addresses concrete ontology languages that are particularly important in the context of the Semantic Web. The most recent and predominant ontology languages and formalisms are presented in relation to each other and a selection of them is discussed in more detail.10aArtificial Intelligence1 aBader, Sebastian1 aHolldobler, Steffen1 aWitzel, Andreas1 aHitzler, Pascal uhttp://www.knoesis.org/node/204401324nas a2200133 4500008004100000245005000041210004900091260002300140520092300163100002001086700002301106700002401129856003701153 2007 eng d00aDecidability Under the Well-Founded Semantics0 aDecidability Under the WellFounded Semantics aInnsbruck, Austria3 aThe well-founded semantics (WFS) for logic programs is one of the few major paradigms for closed-world reasoning. With the advent of the Semantic Web, it is being used as part of rule systems for ontology reasoning, and also investigated as to its usefulness as a semantics for hybrid systems featuring combined open- and closed-world reasoning. Even in its most basic form, however, the WFS is undecidable. In fact, it is not even semi-decidable, which means that it is a theoretical impossibility that sound and complete reasoners for the WFS exist. Surprisingly, however, this matter has received next to no attention in research, although it has already been shown in 1995 by John Schlipf [1]. In this paper, we present several conditions under which query-answering under the well-founded semantics is decidable or semi-decidable. To the best of our knowledge, these are the very first results on such conditions.1 aHitzler, Pascal1 aCherchago, Natalia1 aHolldobler, Steffen uhttp://www.knoesis.org/node/120901186nas a2200121 4500008004100000245004500041210004400086260001300130520084200143100002200985700002001007856003701027 2007 eng d00aDescription Logic Programs: Normal Forms0 aDescription Logic Programs Normal Forms bFAInt-073 aThe relationship and possible interplay between different knowledge representation and reasoning paradigms is a fundamental topic in artificial intelligence. For expressive knowledge representation for the Semantic Web, two different paradigms - namely Description Logics (DLs) and Logic Programming - are the two most successful approaches. A study of their exact relationships is thus paramount. An intersection of OWL with (function-free non-disjunctive) Datalog, called DLP (for Description Logic Programs), has been described in [1,2]. We provide normal forms for DLP in Description Logic syntax and in Datalog syntax, thus providing a bridge for the researcher and user who is familiar with either of these paradigms. We argue that our normal forms are the most convenient way to define DLP for teaching and dissemination purposes.1 aEberhart, Andreas1 aHitzler, Pascal uhttp://www.knoesis.org/node/183801100nas a2200169 4500008004100000245006200041210006000103260002300163300001200186520059000198100002300788700002100811700002000832700002100852700002000873856003700893 2007 eng d00aEfficient OWL Reasoning with Logic Programs - Evaluations0 aEfficient OWL Reasoning with Logic Programs Evaluations aInnsbruck, Austria a370-3733 aWe report on efficiency evaluations concerning two different approaches to using logic programming for OWL [1] reasoning and show, how the two approaches can be combined. Introduction. Scalability of reasoning remains one of the major obstacles in leveraging the full power of the Web Ontology Language OWL [1] for practical applications. Among the many possible approaches to address scalability, one of them concerns the use of logic programming for this purpose. It was recently shown that reasoning in Horn-SHIQ [2-4] can be realised by invoking Prolog systems on the output of the1 aRudolph, Sebastian1 aKrotzsch, Markus1 aSintek, Michael1 aVrandecic, Denny1 aHitzler, Pascal uhttp://www.knoesis.org/node/120501203nas a2200133 4500008004100000245006300041210006300104260003200167300001200199520078300211100001800994700002001012856003701032 2007 eng d00aFoundations of Refinement Operators for Description Logics0 aFoundations of Refinement Operators for Description Logics aCorvallis, OR, USAc06/2007 a161-1743 aIn order to leverage techniques from Inductive Logic Programming for the learning in description logics (DLs), which are the foundation of ontology languages in the Semantic Web, it is important to acquire a thorough understanding of the theoretical potential and limitations of using refinement operators within the description logic paradigm. In this paper, we present a comprehensive study which analyses desirable properties such operators should have. In particular, we show that ideal refinement operators in general do not exist, which is indicative of the hardness inherent in learning in DLs. We also show which combinations of desirable properties are theoretically possible, thus providing an important step towards the definition of practically applicable operators.1 aLehmann, Jens1 aHitzler, Pascal uhttp://www.knoesis.org/node/125800904nas a2200157 4500008004100000245008100041210006900122260002100191300001200212520040000224100002100624700002400645700002000669700002000689856003700709 2007 eng d00aA Fully Connectionist Model Generator for Covered First-Order Logic Programs0 aFully Connectionist Model Generator for Covered FirstOrder Logic aHyderabad, India a666-6713 aWe present a fully connectionist system for the learning of first-order logic programs and the generation of corresponding models: Given a program and a set of training examples, we embed the associated semantic operator into a feed-forward network and train the network using the examples. This results in the learning of first-order knowledge while damaged or noisy data is handled gracefully.1 aBader, Sebastian1 aHolldobler, Steffen1 aWitzel, Andreas1 aHitzler, Pascal uhttp://www.knoesis.org/node/120600333nas a2200097 4500008004100000245005900041210005700100100002100157700002000178856003700198 2007 eng d00aKursarbeit mit Schulern - die Intensivkurse Mathematik0 aKursarbeit mit Schulern die Intensivkurse Mathematik1 aKalmbach, Gudrun1 aHitzler, Pascal uhttp://www.knoesis.org/node/204900841nas a2200145 4500008004100000245008500041210006900126260002200195520037700217100001200594700001500606700001700621700002000638856003700658 2007 eng d00aMeasuring Inconsistency for Description Logics Based on Paraconsistent Semantics0 aMeasuring Inconsistency for Description Logics Based on Paracons aHammamet, Tunisia3 aIn this paper, we present an approach for measuring inconsistency in a knowledge base.We first define the degree of inconsistency using a four-valued semantics for the description logic ALC. Then an ordering over knowledge bases is given by considering their inconsistency degrees. Our measure of inconsistency can provide important information for inconsistency handling.1 aMa, Yue1 aQi, Guilin1 aLin, Zuoquan1 aHitzler, Pascal uhttp://www.knoesis.org/node/121600887nas a2200145 4500008004100000245008500041210006900126260006800195520037700263100001200640700001500652700002000667700001700687856003700704 2007 eng d00aMeasuring Inconsistency for Description Logics Based on Paraconsistent Semantics0 aMeasuring Inconsistency for Description Logics Based on Paracons bthe 2007 International Workshop on Description Logics (DL-2007)3 aIn this paper, we present an approach for measuring inconsistency in a knowledge base.We first define the degree of inconsistency using a four-valued semantics for the description logic ALC. Then an ordering over knowledge bases is given by considering their inconsistency degrees. Our measure of inconsistency can provide important information for inconsistency handling.1 aMa, Yue1 aQi, Guilin1 aHitzler, Pascal1 aLin, Zuoquan uhttp://www.knoesis.org/node/183500938nas a2200133 4500008004100000245006500041210006400106260006800170520048000238100001200718700001700730700002000747856003700767 2007 eng d00aParaconsistent Resolution for Four-valued Description Logics0 aParaconsistent Resolution for Fourvalued Description Logics bthe 2007 International Workshop on Description Logics (DL-2007)3 aIn this paper, we propose an approach to translating any *ALC* ontology (possible inconsistent) into a logically consistent set of disjunctive datalog rules. We achieve this in two steps: First we give a simple way to make any *ALC* based ontology 4-valued satisfiable, and then we study a sound and complete paraconsistent ordered-resolution decision procedure for our 4-valued *ALC*. Our approach can be viewed as a paraconsistent version of KAON2 algorithm.1 aMa, Yue1 aLin, Zuoquan1 aHitzler, Pascal uhttp://www.knoesis.org/node/183700899nas a2200133 4500008004100000245008600041210006900127260001800196520045000214100002300664700002100687700002000708856003700728 2007 eng d00aQuo Vadis, CS? - On the (non)-impact of Conceptual Structures on the Semantic Web0 aQuo Vadis CS On the nonimpact of Conceptual Structures on the Se aSheffield, UK3 aConceptual Structures is a field of research which shares abstract concepts and interests with recent work on knowledge representation for the Semantic Web. However, while the latter is an area of research and development which is rapidly expanding in recent years, the former fails to participate in these developments on a large scale. In this paper, we attempt to stimulate the Conceptual Structures community to catch the Semantic Web train.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/121801081nas a2200133 4500008004100000245008100041210006900122260007300191300001200264520059600276100001800872700002000890856003700910 2007 eng d00aA Refinement Operator Based Learning Algorithm for the ALC Description Logic0 aRefinement Operator Based Learning Algorithm for the ALC Descrip aCorvallis, OR, USAb17th International Conference, ILP 2007c06/2007 a147-1603 aWith the advent of the Semantic Web, description logics have become one of the most prominent paradigms for knowledge representation and reasoning. Progress in research and applications, however, faces a bottleneck due to the lack of available knowledge bases, and it is paramount that suitable automated methods for their acquisition will be developed. In this paper, we provide the first learning algorithm based on refinement operators for the most fundamental description logic ALC. We develop the algorithm from thorough theoretical foundations and report on a prototype implementation.1 aLehmann, Jens1 aHitzler, Pascal uhttp://www.knoesis.org/node/125901362nas a2200145 4500008004100000245007200041210006900113260009900182300000900281520082400290100002001114700002501134700002001159856003701179 2007 eng d00aTowards Tractable Local Closed World Reasoning for the Semantic Web0 aTowards Tractable Local Closed World Reasoning for the Semantic aGuimaraes, Portugalb13th Portuguese Conference on Aritficial Intelligence, EPIA 2007c12/2007 a3-143 aRecently, the logics of minimal knowledge and negation as failure MKNF [12] was used to introduce hybrid MKNF knowledge bases [14], a powerful formalism for combining open and closed world reasoning for the Semantic Web. We present an extension based on a new three-valued framework including an alternating fixpoint, the well-founded MKNF model. This approach, the well-founded MKNF semantics, derives its name from the very close relation to the corresponding semantics known from logic programming. We show that the well-founded MKNF model is the least model among all (three-valued) MKNF models, thus soundly approximating also the two-valued MKNF models from [14]. Furthermore, its computation yields better complexity results (up to polynomial) than the original semantics where models usually have to be guessed.1 aKnorr, Matthias1 aAlferes, Jose, Julio1 aHitzler, Pascal uhttp://www.knoesis.org/node/126301113nas a2200133 4500008004100000245006100041210005800102260006800160520064900228100002000877700002500897700002000922856003700942 2007 eng d00aA Well-founded Semantics for Hybrid MKNF Knowledge Bases0 aWellfounded Semantics for Hybrid MKNF Knowledge Bases bthe 2007 International Workshop on Description Logics (DL-2007)3 aIn [10], hybrid MKNF knowledge bases have been proposed for combining open and closed world reasoning within the logics of minimal knowledge and negation as failure ([8]). For this powerful framework, we define a three-valued semantics and provide an alternating fixpoint construction for nondisjunctive hybrid MKNF knowledge bases. We thus provide a well-founded semantics which is a sound approximation of the cautious MKNF model semantics, and which also features improved computational properties. We also show that whenever the DL knowledge base part is empty, then the alternating fixpoint coincides with the classical well-founded model.1 aKnorr, Matthias1 aAlferes, Jose, Julio1 aHitzler, Pascal uhttp://www.knoesis.org/node/183401394nas a2200133 4500008004100000245004900041210004200090260006400132520096300196100002301159700002101182700002001203856003701223 2006 eng d00aOn the Complexity of Horn Description Logics0 aComplexity of Horn Description Logics bSecond Workshop OWL - Experiences and Directions, OWLED20063 aHorn-*SHIQ* has been identified as a fragment of the description logic *SHIQ* for which inferencing is in PT_{IME} with respect to the size of the ABox. This enables reasoning with larger ABoxes in situations where the TBox is static, and represents one approach towards tractable description logic reasoning. In this paper, we show that reasoning in Horn-*SHIQ*, in spite of its low datacomplexity, is E_{xp}T_{IME}-hard with respect to the overall size of the knowledge base. While this result is not unexpected, the proof is not a mere modification of existing reductions since it has to account for the restrictions of Hornness. We establish the result for Horn-*FLE*, showing that Hornness does not simplify TBox reasoning even for very restricted description logics. Moreover, we derive a context-free grammar that defines Horn-*SHIQ* in a simpler and more intuitive way than existing characterisations.1 aRudolph, Sebastian1 aKrotzsch, Markus1 aHitzler, Pascal uhttp://www.knoesis.org/node/184101382nas a2200157 4500008004100000245005700041210005700098260002000155300001000175520093200185100001701117700001801134700001501152700002001167856003701187 2006 eng d00aHow to Reason with OWL in a Logic Programming System0 aHow to Reason with OWL in a Logic Programming System aAthens, Georgia a17-263 aLogic programming has always been a major ontology modeling paradigm, and is frequently being used in large research projects and industrial applications, e.g., by means of the F-Logic reasoning engine OntoBroker or the TRIPLE query, inference, and transformation language and system. At the same time, the Web Ontology Language OWL has been recommended by the W3C for modeling ontologies for the web. Naturally, it is desirable to investigate the interoperability between both paradigms. In this paper, we do so by studying an expressive fragement of OWL DL for which reasoning can be reduced to the evaluation of Horn logic programs. Building on the KAON2 algorithms for transforming OWL DL into disjunctive Datalog, we give a detailed account of how and to what extent OWL DL can be employed in standard logic programming systems. En route, we derive a novel, simplified characterization of the supported fragment of OWL DL.1 aKrotzsch, M.1 aVrandecic, D.1 aSintek, M.1 aHitzler, Pascal uhttp://www.knoesis.org/node/121100942nas a2200157 4500008004100000245005600041210005600097260002200153520047400175100002400649700002000673700001800693700001900711700001700730856003700747 2006 eng d00aIntegrating Semantic Web Services for Mobile Access0 aIntegrating Semantic Web Services for Mobile Access aBudva, Montenegro3 aWe present our work in integrating Semantic Web services for access via mobile devices. We have developed a system, the WebServiceAccessComponent, that transforms a user request for a service on a mobile device, to a Web service request and then selects a matching service from the existing Web services of the Deutsche Telekom, which provide navigational and weather information. In this poster, we present the requirements and design of the WebServiceAccessComponent.1 aAnkolekar, Anupriya1 aHitzler, Pascal1 aLewen, Holger1 aOberle, Daniel1 aStuder, Rudi uhttp://www.knoesis.org/node/200700773nas a2200157 4500008004100000245006800041210006500109260002200174300001200196520030300208100001500511700001800526700001400544700002000558856003700578 2006 eng d00aA Metamodel and UML Profile for Rule-extended OWL DL Ontologies0 aMetamodel and UML Profile for Ruleextended OWL DL Ontologies aBudva, Montenegro a303-3163 aIn this paper we present a MOF compliant metamodel and UML profile for the Semantic Web Rule Language (SWRL) that integrates with our previous work on a metamodel and UML profile for OWL DL. Based on this metamodel and profile, UML tools can be used for visual modeling of rule-extended ontologies.1 aStuder, R.1 aBrockmans, S.1 aHaase, P.1 aHitzler, Pascal uhttp://www.knoesis.org/node/121300993nas a2200133 4500008004100000245005400041210005400095260002100149300001200170520060300182100001700785700002000802856003700822 2006 eng d00aQuerying Formal Contexts with Answer Set Programs0 aQuerying Formal Contexts with Answer Set Programs aAalborg, Denmark a260-2733 aRecent studies showed how a seamless integration of formal concept analysis (FCA), logic of domains, and answer set programming (ASP) can be achieved. Based on these results for combining hierarchical knowledge with classical rule-based formalisms, we introduce an expressive common-sense query language for formal contexts. Although this approach is conceptually based on order-theoretic paradigms, we show how it can be implemented on top of standard ASP systems. Advanced features, such as default negation and disjunctive rules, thus become practically available for processing contextual data.1 aKrotzsch, M.1 aHitzler, Pascal uhttp://www.knoesis.org/node/121001614nas a2200157 4500008004100000245002900041210002700070300000800097520123400105653000701339653002001346100001501366700001801381700002001399856003701419 2006 eng d00aA Semantic Future for AI0 aSemantic Future for AI a8-93 aIn our modern information society, people need to manage ever-increasing numbers of personal devices and conduct more of their work and activities online, often making use of heterogeneous services. The amount of information to be processed by each individual is constantly growing, making it increasingly difficult to control, channel, share and make constructive use of it. To mitigate this, computing needs to become much more human-centered, e.g. by presenting personalised information to users and by respecting personal preferences in controlling multiple devices or invoking various services. Appropriate representation of the semantics of the information and functionality of devices and services will be critical to such personalised computing. Symbolic artificial intelligence (AI) techniques provide the method of choice for the required semantic representation and reasoning capabilities. The challenge for symbolic AI is to be able to support large-scale, distributed, dynamic knowledge bases enabling highly adaptive and evolving systems. AI must also look to specific application contexts and develop real-world solutions for problems in those domains. Below, we present some examples of such application contexts.10aAI10aSemantics of AI1 aStuder, R.1 aAnkolekar, A.1 aHitzler, Pascal uhttp://www.knoesis.org/node/162400929nas a2200133 4500008004100000245005200041210005200093520052700145100001700672700002300689700002600712700002000738856003700758 2006 eng d00aVisual Ontology Modeling for Electronic Markets0 aVisual Ontology Modeling for Electronic Markets3 aThe research program, Information Management and Market Engineering, focuses on the analysis and the design of electronic markets. Taking a holistic view of the conceptualization and realization of solutions, the research integrates the disciplines business administration, economics, computer science, and law. Topics of interest range from the implementation, quality assurance, and further development of electronic markets to their integration into business processes, innovative business models, and legal frameworks.1 aStuder, Rudi1 aBrockmans, Saartje1 aGeyer-Schulz, Andreas1 aHitzler, Pascal uhttp://www.knoesis.org/node/204300337nas a2200085 4500008004100000245008400041210006900125100002000194856003700214 2005 eng d00aAutomatisiertes Schließen mit formalen Begriffen: Mathematische Grundlagen0 aAutomatisiertes Schlie223en mit formalen Begriffen Mathematische1 aHitzler, Pascal uhttp://www.knoesis.org/node/205000334nas a2200085 4500008004100000245008000041210007000121100002000191856003700211 2005 eng d00aAutomatisiertes Schließen mit formalen Begriffen: Mathematische Grundlagen0 aAutomatisiertes Schließen mit formalen Begriffen Mathematische G1 aHitzler, Pascal uhttp://www.knoesis.org/node/242800849nas a2200145 4500008004100000245004900041210004900090260005600139520039800195100001700593700001900610700001700629700002000646856003700666 2005 eng d00aBridging the Paradigm Gap with Rules for OWL0 aBridging the Paradigm Gap with Rules for OWL bW3C Workshop on Rule Languages for Interoperability3 aAccelerated by the vision of the semantic web, semantic technologies have recently made significant advances. The underlying methods and paradigms are already being transferred to adjacent areas of research in artificial intelligence, knowledge management, and elsewhere. Textbooks explaining the foundations have appeared. Large national and international projects on the topic are under way.1 aStuder, Rudi1 aAngele, Jurgen1 aMotik, Boris1 aHitzler, Pascal uhttp://www.knoesis.org/node/181001469nas a2200133 4500008004100000245007900041210006900120260003500189520100600224100002101230700002701251700002001278856003701298 2005 eng d00aComputing First-Order Logic Programs by Fibring Artificial Neural Networks0 aComputing FirstOrder Logic Programs by Fibring Artificial Neural aClearwater Beach, Florida, USA3 aThe integration of symbolic and neural-network-based artificial intelligence paradigms constitutes a very challenging area of research. The overall aim is to merge these two very different major approaches to intelligent systems engineering while retaining their respective strengths. For symbolic paradigms that use the syntax of some first-order language this appears to be particularly difficult. In this paper, we will extend on an idea proposed by Garcez and Gabbay (2004) and show how first-order logic programs can be represented by fibred neural networks. The idea is to use a neural network to iterate a global counter n. For each clause C_{i} in the logic program, this counter is combined (fibred) with another neural network, which determines whether C_{i} outputs an atom of level *n* for a given interpretation *I*. As a result, the fibred network computes the singlestep operator T_{P} of the logic program, thus capturing the semantics of the program.1 aBader, Sebastian1 aGarcez, Artur, S. D'A.1 aHitzler, Pascal uhttp://www.knoesis.org/node/120001560nas a2200133 4500008004100000245008300041210006900124260007000193520107400263100001501337700001701352700002001369856003701389 2005 eng d00aDescription Logic Programs: A Practical Choice For the Modelling of Ontologies0 aDescription Logic Programs A Practical Choice For the Modelling b1st Workshop on Formal Ontologies meet Meet Industry, FOMI'053 aKnowledge representation using ontologies constitutes the heart of semantic technologies. Despite successful standardization e.orts by the W3C, however, there are still numerous di.erent ontology representation languages being used, and interoperability between them is in general not given. The problem is aggrevated by the fact that current standards lay foundations only and are well-known to be insufficient for the modelling of finer details. Thus, a plethora of extensions of the basic languages is being proposed, rendering the picture of ontology representation languages to be chaotic, to say the least. While semantic technologies start to become applicable and are being applied in adjacent areas of research and in research projects with industrial participation, and can soon be expected to become an integral part of industrial applications, the practitioner is faced with the difficult task of choosing his basic ontology representation paradigm. We will argue that the OWL subset known as Description Logic Programs constitutes a very reasonable choice.1 aSure, York1 aStuder, Rudi1 aHitzler, Pascal uhttp://www.knoesis.org/node/181200350nas a2200097 4500008004100000245006800041210006500109100002100174700002000195856003700215 2005 eng d00aDimensions of Neural-Symbolic Integration - A Structured Survey0 aDimensions of NeuralSymbolic Integration A Structured Survey1 aBader, Sebastian1 aHitzler, Pascal uhttp://www.knoesis.org/node/204500615nas a2200145 4500008004100000245003500041210003200076520023400108100001500342700001700357700002100374700001700395700002000412856003700432 2005 eng d00aDLP Isn't So Bad After All0 aDLP Isn39t So Bad After All3 aWe discuss some of the recent controversies concerning the DLP fragment of OWL. We argue that it is a meaningful fragment and can serve as a basic interoperability layer between OWL and logic programming-based ontology languages.1 aSure, York1 aStuder, Rudi1 aKrotzsch, Markus1 aHaase, Peter1 aHitzler, Pascal uhttp://www.knoesis.org/node/184000363nas a2200133 4500008004100000245003100041210003000072100002000102700001500122700001700137700002100154700001700175856003700192 2005 eng d00aDLP Isn't So Bad After All0 aDLP Isnt So Bad After All1 aHitzler, Pascal1 aSure, York1 aStuder, Rudi1 aKrotzsch, Markus1 aHaase, Peter uhttp://www.knoesis.org/node/232100776nas a2200109 4500008004100000245003600041210003600077520047500113100002100588700002000609856003700629 2005 eng d00aFaster OWL Using Split Programs0 aFaster OWL Using Split Programs3 aKnowledge representation and reasoning on the Semantic Web is done by means of ontologies. While the quest for suitable ontology languages is still ongoing, OWL [5] has been established as a core standard. It comes in three flavours, as OWL Full, OWL DL and OWL Lite, where OWL Full contains OWL DL, which in turn contains OWL Lite. The latter two coincide semantically with certain description logics and can thus be considered fragments of first-order predicate logic.1 aVrandecic, Denny1 aHitzler, Pascal uhttp://www.knoesis.org/node/180701032nas a2200133 4500008004100000245008400041210006900125260005200194520054400246653003000790100002100820700002000841856003700861 2005 eng d00aLevel Mapping Characterizations of Selector-Generated Models for Logic Programs0 aLevel Mapping Characterizations of SelectorGenerated Models for b19th Workshop on (Constraint) Logic Programming3 aAssigning semantics to logic programs via selector generated models (Schwarz 2002/2003) extends several semantics, like the stable, the inflationary, and the stable generated semantics, to programs with arbitrary formulae in rule heads and bodies. We study this approach by means of a unifying framework for characterizing different logic programming semantics using level mappings (Hitzler and Wendt 200x, Hitzler 2003), thereby supporting the claim that this framework is very flexible and applicable to very diversely defined semantics.10aSelector-Generated Models1 aSchwarz, Sibylle1 aHitzler, Pascal uhttp://www.knoesis.org/node/179101057nas a2200109 4500008004100000245004900041210004900090520073100139100002000870700002000890856003700910 2005 eng d00aModeling Fuzzy Rules with Description Logics0 aModeling Fuzzy Rules with Description Logics3 aIn real application scenarios, input data and knowledge is often vague. Likewise, it is often the case that exact reasoning over data is impossible due to complex dependencies between input data and target outputs. For practical applications, however, good approximations often suffice, and efficient calculation of an approximate answer is often preferable over complex processing which may take a long time to come up with an exact answer. Fuzzy logic supports both features by providing fuzzy membership functions and fuzzy IF-THEN rule bases. In this paper, we show how fuzzy membership functions and fuzzy rules can be modeled by means of an appropriate description logic and how this can be employed for query answering.1 aAgarwal, Sudhir1 aHitzler, Pascal uhttp://www.knoesis.org/node/183901226nas a2200145 4500008004100000245002500041210002500066260002000091300001200111520085800123100002100981700002101002700002001023856003701043 2005 eng d00aMorphisms in Context0 aMorphisms in Context aKassel, Germany a223-2373 aMorphisms constitute a general tool for modelling complex relationships between mathematical objects in a disciplined fashion. In Formal Concept Analysis (FCA), morphisms can be used for the study of structural properties of knowledge represented in formal contexts, with applications to data transformation and merging. In this paper we present a comprehensive treatment of some of the most important morphisms in FCA and their relationships, including dual bonds, scale measures, infomorphisms, and their respective relations to Galois connections. We summarize our results in a concept lattice that cumulates the relationships among the considered morphisms. The purpose of this work is to lay a foundation for applications of FCA in ontology research and similar areas, where morphisms help formalize the interplay among distributed knowledge bases.1 aKrotzsch, Markus1 aZhang, Guo-Qiang1 aHitzler, Pascal uhttp://www.knoesis.org/node/119900756nas a2200121 4500008004100000245006800041210006700109520035000176100002100526700003000547700002000577856003700597 2005 eng d00aOntology Learning as a Use Case for Neural-Symbolic Integration0 aOntology Learning as a Use Case for NeuralSymbolic Integration3 aWe argue that the field of neural-symbolic integration is in need of identifying application scenarios for guiding further research. We furthermore argue that ontology learning - as occuring in the context of semantic technologies - provides such an application scenario with potential for success and high impact on neural-symbolic integration.1 aBader, Sebastian1 aGarcez, Artur, S. D'Avila1 aHitzler, Pascal uhttp://www.knoesis.org/node/231801024nas a2200133 4500008004100000245005400041210005300095260002000148300001200168520063200180100002100812700002000833856003700853 2005 eng d00aResolution-based approximate reasoning for OWL DL0 aResolutionbased approximate reasoning for OWL DL aGalway, Ireland a383-3973 aWe propose a new technique for approximate ABox reasoning with OWL DL ontologies. Essentially, we obtain substantially improved reasoning performance by disregarding non-Horn features of OWL DL. Our approach comes as a side-product of recent research results concerning a new transformation of OWL DL ontologies into negation-free disjunctive datalog [1, 2, 3, 4], and rests on the idea of performing standard resolution over disjunctive rules by treating them as if they were non-disjunctive ones. We analyse our reasoning approach by means of non-monotonic reasoning techniques, and present an implementation, called Screech.1 aVrandecic, Denny1 aHitzler, Pascal uhttp://www.knoesis.org/node/121201858nas a2200181 4500008004100000245007600041210006900117260006100186520125200247100001901499700002201518700001701540700002001557700001901577700002301596700002001619856003701639 2005 eng d00aSemantic Management of Web Services using the Core Ontology of Services0 aSemantic Management of Web Services using the Core Ontology of S bW3C Workshop on Frameworks for Semantics in Web Services3 aDifferent Web Service standards like WSDL, WS-Security, WS-Policy etc., henceforth referred to as WS*, factorize Web Service management tasks into different aspects, such as input/output, workflow, or security. The advantages of WS* are multiple and have already achieved industrial impact. WS* descriptions are exchangeable and developers may use different implementations for the same Web Service description. The disadvantages of WS*, however, are also apparent: even though the different standards are complementary, they must overlap and one may produce models composed of different WS* descriptions, which are inconsistent with each other, but the reasons for the inconsistencies are not easily determined. This is the case because there is no coherent conceptual model of WS*, i.e. terms with equivalent semantics are introduced differently in the respective XML-DTDs. Thus, it is impossible to ask for conclusions that come from integrating different WS* descriptions. Hence, discovering such Web Service management problems or asking for other similar kinds of conclusions that derive from the integration of WS* descriptions remains a purely manual task to be done by the software developers accompanied by little to no formal machinery.1 aGrimm, Stephan1 aEberhart, Andreas1 aStuder, Rudi1 aAgarwal, Sudhir1 aOberle, Daniel1 aLamparter, Steffen1 aHitzler, Pascal uhttp://www.knoesis.org/node/181300385nas a2200145 4500008004100000245003200041210002800073300001000101653001700111100001500128700002200143700001700165700002000182856003700202 2005 eng d00aThe Semantic Web in One Day0 aSemantic Web in One Day a85-8710aSemantic Web1 aSure, York1 aEberhart, Andreas1 aStuder, Rudi1 aHitzler, Pascal uhttp://www.knoesis.org/node/163401035nas a2200145 4500008004100000245007500041210006900116300001200185520055900197653002800756653002200784653002600806100002000832856003700852 2005 eng d00aTowards a Systematic Account of Different Semantics for Logic Programs0 aTowards a Systematic Account of Different Semantics for Logic Pr a391-4043 aIn [1,2], a new methodology has been proposed which allows to derive uniform characterizations of different declarative semantics for logic programs and negation. One result from this work is that the well-founded semantics can formally be understood as a stratified version of Fitting (or Kripke Kleene) semantics. The construction leading to this result, however, show a certain asymmetry which is not readily understood. We will study this situation here with the result that we will obtain a coherent picture of relations between different semantics.10aKripke Kleene semantics10alogic programming10aprogramming semantics1 aHitzler, Pascal uhttp://www.knoesis.org/node/163301419nas a2200133 4500008004100000245005400041210005200095300001200147520101700159653003201176100002001208700002001228856003701248 2005 eng d00aA uniform approach to logic programming semantics0 auniform approach to logic programming semantics a123-1593 aPart of the theory of programming and nonymonotonic reasoning concerns the study of fixed-point semantics for these paradigms. Several different semantics have been proposed during the last two decades, and some have been more successful and acknowledged than others. The rationales behind those various semantics have been manifold, depending on one's point of view, which may be that of a programmer or inspired by commonsense reasoning, and consequently the constructions which lead to these semantics are technically very diverse, and the exact relationships between them have not yet been fully understood. In this paper, we present a conceptually new method, based on level mappings, which allows to provide uniform characterizations of different semantics for logic programs. We will display our approach by giving new and uniform characterizations of some of the major semantics, and of the well-founded semantics. A novel characterization of the weakly perfect model semantics will also be provided.10alogic programming semantics1 aWendt, Matthias1 aHitzler, Pascal uhttp://www.knoesis.org/node/163201732nas a2200157 4500008004100000245007700041210006900118260002000187300001200207520124500219100001401464700002501478700001401503700002001517856003701537 2005 eng d00aThe Well-Supported Semantics for Multidimensional Dynamic Logic Programs0 aWellSupported Semantics for Multidimensional Dynamic Logic Progr aDiamante, Italy a356-3683 aMultidimensional dynamic logic programs are a paradigm which allows to express (partially) hierarchically ordered evolving knowledge bases through (partially) ordered multi sets of logic programs and allowing to solve contradictions among rules in different programs by allowing rules in more important programs to reject rules in less important ones. This class of programs extends the class of dynamic logic program that provides meaning and semantics to sequences of logic programs. Recently a semantics named refined stable model semantics has fixed some counterintuitive behaviour of previously existing semantics for dynamic logic programs. However, it is not possible to directly extend the definitions and concepts of the refined semantics to the multidimensional case and hence more sophisticated principles and techniques are in order. In this paper we face the problem of defining a proper semantics for multidimensional dynamic logic programs by extending the idea of well supported model to this class of programs and by showing that this concept alone is enough for univocally characterizing a proper semantics. We then show how the newly defined semantics coincides with the refined one when applied to sequences of programs.1 aBanti, F.1 aAlferes, Jose, Julio1 aBrogi, A.1 aHitzler, Pascal uhttp://www.knoesis.org/node/119802377nas a2200145 4500008004100000245008200041210006900123260006500192520186500257100001502122700002102137700001602158700002002174856003702194 2005 eng d00aWhat Is Ontology Merging? - A Category-Theoretical Perspective Using Pushouts0 aWhat Is Ontology Merging A CategoryTheoretical Perspective Using b20th National Conference on Artificial Intelligence, AAAI-053 aIn this paper we explain how merging of ontologies is captured by the pushout construction from category theory, and argue that this is a very natural approach to the problem. We study this independent of a specific choice of ontology representation language, and thus provide a sort of blueprint for the development of algorithms applicable in practice. For this purpose, we view category theory as a universal 'meta specification language' that enables us to specify properties of ontological relationships and constructions in a way that does not depend on any particular implementation. This can be achieved since the basic objects of study in category theory are the relationships between multiple ontological specifications, not the internal structure of a single knowledge representation. Categorical pushouts are already considered in some approaches to ontology research (Jannink et al. 1998; Schorlemmer, Potter, & Robertson 2002; Goguen 2005; Kent 2005) and we do not claim our treatment to be entirely original. Still we have the impression that the potential of category theoretic approaches is by far not exhausted in todays ontology research. For our particular case the treatment will focus on the ontology merging, for which we will give both intuitive explanations and precise definitions. This reflects our belief that, at the current stage of research, it is not desirable to fade out the mathematical details of the categorical approach completely, since the interfaces to current techniques in ontology research are not yet available to their full extent. We will also keep this treatment rather general, not narrowing the discussion to specific formalisms - this added generality is one of the strengths of category theory. A long version of this paper with a tutorial character is available from the first author's homepage.1 aSure, York1 aKrotzsch, Markus1 aEhrig, Marc1 aHitzler, Pascal uhttp://www.knoesis.org/node/180601378nas a2200109 4500008004100000245006700041210006500108520101700173100002101190700002001211856003701231 2004 eng d00aA cartesian closed category of approximable concept structures0 acartesian closed category of approximable concept structures3 aInfinite contexts and their corresponding lattices are of theoretical and practical interest since they may offer connections with and insights from other mathematical structures which are normally not restricted to the finite cases. In this paper we establish a systematic connection between formal concept analysis and domain theory as a categorical equivalence, enriching the link between the two areas as outlined in [25]. Building on a new notion of approximable concept introduced by Zhang and Shen [26], this paper provides an appropriate notion of morphisms on formal contexts and shows that the resulting category is equivalent to (a) the category of complete algebraic lattices and Scott continuous functions, and (b) a category of information systems and approximable mappings. Since the latter categories are cartesian closed, we obtain a cartesian closed category of formal contexts that respects both the context structures as well as the intrinsic notion of approximable concepts at the same time.1 aZhang, Guo-Qiang1 aHitzler, Pascal uhttp://www.knoesis.org/node/119401105nas a2200097 4500008004100000245005900041210005900100520079100159100002000950856003700970 2004 eng d00aDefault Reasoning over Domains and Concept Hierarchies0 aDefault Reasoning over Domains and Concept Hierarchies3 aW.C. Rounds and G.-Q. Zhang have proposed to study a form of disjunctive logic programming generalized to algebraic domains [1]. This system allows reasoning with information which is hierarchically structured and forms a (suitable) domain. We extend this framework to include reasoning with default negation, giving rise to a new nonmonotonic reasoning framework on hierarchical knowledge which encompasses answer set programming with extended disjunctive logic programs. We also show that the hierarchically structured knowledge on which programming in this paradigm can be done, arises very naturally from formal concept analysis. Together, we obtain a default reasoning paradigm for conceptual knowledge which is in accordance with mainstream developments in nonmonotonic reasoning.1 aHitzler, Pascal uhttp://www.knoesis.org/node/119301270nas a2200133 4500008004100000245013500041210006900176260001700245520077200262100002101034700002401055700002001079856003701099 2004 eng d00aThe Integration of Connectionism and First-Order Knowledge Representation and Reasoning as a Challenge for Artificial Intelligence0 aIntegration of Connectionism and FirstOrder Knowledge Representa aTokyo, Japan3 aIntelligent systems based on first-order logic on the one hand, and on artificial neural networks (also called connectionist systems) on the other, differ substantially. It would be very desirable to combine the robust neural networking machinery with symbolic knowledge representation and reasoning paradigms like logic programming in such a way that the strengths of either paradigm will be retained. Current state-of-the-art research, however, fails by far to achieve this ultimate goal. As one of the main obstacles to be overcome we perceive the question how symbolic knowledge can be encoded by means of connectionist systems: Satisfactory answers to this will naturally lead the way to knowledge extraction algorithms and to integrated neural-symbolic systems.1 aBader, Sebastian1 aHolldobler, Steffen1 aHitzler, Pascal uhttp://www.knoesis.org/node/119200370nas a2200097 4500008004100000245008400041210006900125100002100194700002000215856003700235 2004 eng d00aLevel mapping characterizations of selector-generated models for logic programs0 aLevel mapping characterizations of selectorgenerated models for 1 aSchwarz, Sibylle1 aHitzler, Pascal uhttp://www.knoesis.org/node/192001251nas a2200133 4500008004100000245009200041210006900133300001300202520080100215653002301016100002101039700002001060856003701080 2004 eng d00aLogic Programs, Iterated Function Systems, and Recurrent Radial Basis Function Networks0 aLogic Programs Iterated Function Systems and Recurrent Radial Ba a273- 3003 aGraphs of the single-step operator for first-order logic programs -displayed in the real plane - exhibit self-similar structures known from topological dynamics, i.e. they appear to be *fractals*, or more precisely, attractors of iterated function systems. We show that this observation can be made mathematically precise. In particular, we give conditions which ensure that those graphs coincide with attractors of suitably chosen iterated function systems, and conditions which allow the approximation of such graphs by iterated function systems or by fractal interpolation. Since iterated function systems can easily be encoded using recurrent radial basis function networks, we eventually obtain connectionist systems which approximate logic programs in the presence of function symbols.10aiterated functions1 aBader, Sebastian1 aHitzler, Pascal uhttp://www.knoesis.org/node/163501141nas a2200133 4500008004100000245011300041210006900154260002100223300001200244520067200256100002200928700002000950856003700970 2003 eng d00aContinuity of Semantic Operators in Logic Programming and their Approximation by Artificial Neural Networks.0 aContinuity of Semantic Operators in Logic Programming and their aHamburg, Germany a105-1193 aOne approach to integrating First-order logic programming and neural network systems employs the approximation of semantic operators by feedforward networks. For this purpose, it is necessary to view these semantic operators as continuous functions on the reals. This can be accomplished by endowing the space of all interpretations of a logic program with topologies obtained from suitable embeddings. We will present such topologies which arise naturally out of the theory of logic programming, discuss continuity issues of several wellknown semantic operators, and derive some results concerning the approximation of these operators by feedforward neural networks.1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/120401032nas a2200133 4500008004100000245006400041210006400105260002600169300001200195520061400207100002000821700002000841856003700861 2003 eng d00aFormal Concept Analysis and Resolution in Algebraic Domains0 aFormal Concept Analysis and Resolution in Algebraic Domains aShaker Verlag, Aachen a205-2213 aWe relate two formerly independent areas: Formal concept analysis and logic of domains. We will establish a correspondene between contextual attribute logic on formal contexts resp. concept lattices and a clausal logic on coherent algebraic cpos. We show how to identify the notion of formal concept in the domain theoretic setting. In particular, we show that a special instance of the resolution rule from the domain logic coincides with the concept closure operator from formal concept analysis. The results shed light on the use of contexts and domains for knowledge representation and reasoning purposes.1 aWendt, Matthias1 aHitzler, Pascal uhttp://www.knoesis.org/node/119000996nas a2200109 4500008004100000245008500041210006900126520061400195100002000809700002000829856003700849 2003 eng d00aFormal Concept Analysis and Resolution on Algebraic Domains - Preliminary Report0 aFormal Concept Analysis and Resolution on Algebraic Domains Prel3 aWe relate two formerly independent areas: Formal concept analysis and logic of domains. We will establish a correspondene between contextual attribute logic on formal contexts resp. concept lattices and a clausal logic on coherent algebraic cpos. We show how to identify the notion of formal concept in the domain theoretic setting. In particular, we show that a special instance of the resolution rule from the domain logic coincides with the concept closure operator from formal concept analysis. The results shed light on the use of contexts and domains for knowledge representation and reasoning purposes.1 aWendt, Matthias1 aHitzler, Pascal uhttp://www.knoesis.org/node/192501336nas a2200145 4500008004100000245006300041210006300104300001200167520086300179653005201042653001701094100002201111700002001133856003701153 2003 eng d00aGeneralized Metrics and Uniquely Determined Logic Programs0 aGeneralized Metrics and Uniquely Determined Logic Programs a187-2193 aThe introduction of negation into logic programming brings the benefit of enhanced syntax and expressibility, but creates some semantical problems. Specifically, certain operators which are monotonic in the absence of negation become non-monotonic when it is introduced, with the result that standard approaches to denotational semantics then become inapplicable. In this paper, we show how generalized metric spaces can be used to obtain fixed-point semantics for several classes of programs relative tot eh supported model semantics, and investigate relationships between the underlying spaces we employ. Our methods allow the analysis of classes of programs which include the acyclic, locally hierarchical, and acceptable programs amongst others, and draw on fixed-point theorems which apply to generalized ultrametric spaces and to partial metric spaces.10aPriess-Crampe and Ribenboim Fixed-Point Theorem10aUltrametrics1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/163600957nas a2200121 4500008004100000245004700041210004500088260002100133300001400154520061000168100002000778856003700798 2003 eng d00aA Resolution Theorem for Algebraic Domains0 aResolution Theorem for Algebraic Domains aAcapulco, Mexico a1339-13403 aW. C. Rounds and G.-Q. Zhang have recently proposed to study a form of resolution on algebraic domains [Rounds and Zhang, 2001]. This framework allows reasoning with knowledge which is hierarchically structured and forms a (suitable) domain, more precisely, a coherent algebraic cpo as studied in domain theory. In this paper, we give conditions under which a resolution theorem -- in a form underlying resolution-based logic programming systems -- can be obtained. The investigations bear potential for engineering new knowledge representation and reasoning systems on a firm domain-theoretic background.1 aHitzler, Pascal uhttp://www.knoesis.org/node/120101000nas a2200121 4500008004100000245007400041210006900115260002100184300001200205520060400217100002000821856003700841 2003 eng d00aTowards a Systematic Account of Different Logic Programming Semantics0 aTowards a Systematic Account of Different Logic Programming Sema aHamburg, Germany a355-3693 aIn [14, 15], a new methodology has been proposed which allows to derive uniform characterizations of different declarative semantics for logic programs with negation. One result from this work is that the well-founded semantics can formally be understood as a stratiÃ¯Â¬Âed version of the Fitting (or Kripke-Kleene) semantics. The constructions leading to this result, however, show a certain asymmetry which is not readily understood. We will study this situation here with the result that we will obtain a coherent picture of relations between different semantics for normal logic programs.1 aHitzler, Pascal uhttp://www.knoesis.org/node/120200971nas a2200121 4500008004100000245006700041210006700108260004200175520055500217100002000772700002000792856003700812 2002 eng d00aCharacterizing Logic Programming Semantics with Level Mappings0 aCharacterizing Logic Programming Semantics with Level Mappings bWLP: Workshop Logische Programmierung3 aDeclarative semantics in logic programming and nonmonotonic reasoning are often defined via fixed points of semantic operators. While many relationships between different semantics known from the literature have been studied, a uniform treatment is still missing. In this paper, we provide uniform operator-free characterizations for some of the most important semantics, more precisely, for the stable, the well-founded, and the Fitting semantics, for the weakly-perfect model semantics, and for the least model semantics for negation-free programs.1 aWendt, Matthias1 aHitzler, Pascal uhttp://www.knoesis.org/node/179200272nas a2200085 4500008004100000245004500041210004300086100002000129856003700149 2002 eng d00aContexts, Concepts, and Logic of Domains0 aContexts Concepts and Logic of Domains1 aHitzler, Pascal uhttp://www.knoesis.org/node/192300368nas a2200097 4500008004100000245008100041210006900122100002200191700002000213856003700233 2002 eng d00aThe Fixed-Point Theorems of Priess-Crampe and Ribenboim in Logic Programming0 aFixedPoint Theorems of PriessCrampe and Ribenboim in Logic Progr1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/204600422nas a2200121 4500008004100000245005900041210005900100260004200159300001200201100003000213700002000243856003700263 2002 eng d00aILP Operators for Propositional Connectionist Networks0 aILP Operators for Propositional Connectionist Networks aWLP: Workshop Logische Programmierung a103-1061 aGutierrez-Naranjo, Miguel1 aHitzler, Pascal uhttp://www.knoesis.org/node/179301116nas a2200121 4500008004100000245006100041210006100102260004200163520067900205653005300884100002000937856003700957 2002 eng d00aTowards Nonmonotonic Reasoning on Hierarchical Knowledge0 aTowards Nonmonotonic Reasoning on Hierarchical Knowledge bWLP: Workshop Logische Programmierung3 aW.C. Rounds and G.Q. Zhang have recently proposed to study a form of disjunctive logic programming generalized to algebraic domains [RZ01]. This system allows reasoning with information which is hierarchically structured and forms a (suitable) domain. We extend this framework to include reasoning with negative information, i.e. the implicit or explicit absence of bits of information. These investigations will naturally lead to a form of default reasoning which is strongly related to programming with answer sets to stable models, which has recently created much interest amongst artificial intelligence researchers concerned with knowledge representation and reasoning.10anonmonotonic reasoning and hierarchial knowledge1 aHitzler, Pascal uhttp://www.knoesis.org/node/179500937nas a2200109 4500008004100000245006500041210006000106520058400166100002000750700002000770856003700790 2002 eng d00aThe Well-Founded Semantics is a Stratified Fitting Semantics0 aWellFounded Semantics is a Stratified Fitting Semantics3 aPart of the theory of logic programming and nonmonotonic reasoning concerns the study of fixed-point semantics for these paradigms. While several different semantics have been proposed, and some have been more successful than others, the exact relationships between the approaches have not yet been fully understood. In this paper, we give new characterizations, using level mappings, of the Fitting semantics, the well-founded semantics, and the weakly perfect model semantics. The results will unmask the well-founded semantics as a stratified version of the Fitting semantics.1 aWendt, Matthias1 aHitzler, Pascal uhttp://www.knoesis.org/node/119100983nas a2200145 4500008004100000245006000041210005600101300000800157520053100165653002300696653003900719100002000758700002200778856003700800 2001 eng d00aA "Converse" of the Bananch Contraction Mapping Theorem0 aConverse of the Bananch Contraction Mapping Theorem a3-63 aWe prove a type of converse of the Banach contraction mapping theorem for metric spaces: if X is a T_{1} topological space and *f*: X -> X is a function with the unique fixed point *a* such that *f*^{n}(*x*) converges to *a* for each *x* is a member of *X*, then there exists a distance function *d* on *X* such that *f* is a contraction on the complete ultrametric space (X,d) with contractivity factor 1/2. We explore properties of the resulting space (X,d).10aBanach contraction10aBanach contraction mapping theorem1 aHitzler, Pascal1 aSeda, Anthony, K. uhttp://www.knoesis.org/node/163100308nas a2200085 4500008004100000245006200041210006200103100002000165856003700185 2001 eng d00aKontraktionssatze auf verallgemeinerten metrischen Raumen0 aKontraktionssatze auf verallgemeinerten metrischen Raumen1 aHitzler, Pascal uhttp://www.knoesis.org/node/205501137nas a2200133 4500008004100000245006700041210006600108260002600174300001200200520071200212100002200924700002000946856003700966 2001 eng d00aSemantic Operators and Fixed-Point Theory in Logic Programming0 aSemantic Operators and FixedPoint Theory in Logic Programming aOrlando, Florida, USA a224-2293 aWe consider rather general operators mapping valuations to (sets of) valuations in the context of the semantics of logic programming languages. This notion generalizes several of the standard operators encountered in this subject and is inspired by earlier work of M.C. Fitting. The fixed points of such operators play a fundamental role in logic programming semantics by providing standard models of logic programs and also in determining the computability properties of these standard models. We discuss some of our recent work employing topological ideas, in conjunction with order theory, to establish methods by which one can nd the fixed points of the operators arising in logic programming semantics.1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/118900977nas a2200157 4500008004100000245005300041210005200094300001200146520050300158653002700661653002200688653003000710100002200740700002000762856003700782 2001 eng d00aUnique Supported-Model Classes of Logic Programs0 aUnique SupportedModel Classes of Logic Programs a295-3023 aWe study classes of programs, herein called *unique supported-model classes,* with the property that each program in the class has a unique supported model. Elsewhere, the authors examined these classes from the point of view of operators defined relative to certain three-valued logics. In this paper, we complement our earlier results by considering how unique supported-model classes fit into the framework given by various classes of programs in several well-known approaches to semantics.10adenotational semantics10alogic programming10asupported-model semantics1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/163700415nas a2200109 4500008004100000245006700041210006500108260005700173100001800230700002000248856003700268 2001 eng d00aVDM meets LCF: Domain-Theoretic and Topological Aspects of VDM0 aVDM meets LCF DomainTheoretic and Topological Aspects of VDM bFifth Irish Workshop on Formal Methods (IWFM'01)1 aSeda, Anthony1 aHitzler, Pascal uhttp://www.knoesis.org/node/179401567nas a2200109 4500008004100000245006900041210006800110520120000178100002201378700002001400856003701420 2000 eng d00aClasses of Logic Programs which Possess Unique Supported Models.0 aClasses of Logic Programs which Possess Unique Supported Models3 aLogic programming is concerned with the use of logic as a programming language. The main manifestation of this computing paradigm is in the various versions of Prolog which are now available, in which computation is viewed as deduction from sets of Horn clauses, although there is also growing interest in the related form known as answer set programming, see [10]. The reference [1] contains a good survey of the growth of logic programming over the last twenty-five years both as a stand-alone programming language and as a software component of large information systems. One advantage a logic program P has over conventional imperative and object oriented programs is that it has a natural machine-independent meaning, namely, its logical meaning. This is often referred to as its declarative semantics, and is usually taken to be some 'standard' model canonically associated with P. Unfortunately, it is often the case that there are many possible choices for the standard model, some even taken in many-valued logic, which do not in general coincide and all of which have a claim to be 'the natural choice' depending on one's view of non-monotonic reasoning [6, 7, 11].1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/118501263nas a2200109 4500008004100000245006900041210006200110520090200172100002201074700002001096856003701116 2000 eng d00aOn the Coincidence of Semantics for Uniquely Determined Programs0 aCoincidence of Semantics for Uniquely Determined Programs3 aWe study classes of logic programs, called here unique supported model classes or simply usm- classes, with the property that each member in the class is uniquely determined, that is, possesses a unique supported model. Known classes of uniquely determined programs include the acyclic and the acceptable programs, which have been much studied in the context of termination, and the authors gave a unifying treatment of these and other unique supported model classes in an earlier paper. In the present paper, we complement these earlier results by considering how various standard semantics relate to each other within certain unique supported model classes. In particular, we introduce the natural usm-class of all accessible programs, which contains the aforementioned classes, and has the property that, for each member of it, the stable, well-founded and weakly perfect-a models all coincide.1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/118800348nas a2200097 4500008004100000245006500041210006400106100002300170700002000193856003700213 2000 eng d00aDer Banachsche Fixpunktsatz und der Satz von Picard-Lindelof0 aDer Banachsche Fixpunktsatz und der Satz von PicardLindelof1 aLutscher, Frithjof1 aHitzler, Pascal uhttp://www.knoesis.org/node/204101059nas a2200133 4500008004100000245002600041210002600067520071500093653002300808653001500831100002000846700002200866856003700888 2000 eng d00aDislocated Topologies0 aDislocated Topologies3 aWe study a generalized notion of topology which evolved out of applications in the area of logic programming semantics. The generalization is obtained by relaxing the requirements that a neighbourhood of a point includes the point itself, and by allowing neighbourhoods of points to be empty. The correspoding generalized notion of metric is obtained by allowing points to have non-zero distance to themselves. We further show that it is meaningful to discuss neightbourhoods, convergence, and continuity in these spaces. A generalized version of the Banach contraction mapping theorem can also be established. We show finally how the generalized metrics studied here can be obtained from conventional metrics.10aBanach contraction10atopologies1 aHitzler, Pascal1 aSeda, Anthony, K. uhttp://www.knoesis.org/node/163001027nas a2200121 4500008004100000245002600041210002600067520071500093100002000808700001800828700002200846856003700868 2000 eng d00aDislocated Topologies0 aDislocated Topologies3 aWe study a generalized notion of topology which evolved out of applications in the area of logic programming semantics. The generalization is obtained by relaxing the requirements that a neighbourhood of a point includes the point itself, and by allowing neighbourhoods of points to be empty. The correspoding generalized notion of metric is obtained by allowing points to have non-zero distance to themselves. We further show that it is meaningful to discuss neightbourhoods, convergence, and continuity in these spaces. A generalized version of the Banach contraction mapping theorem can also be established. We show finally how the generalized metrics studied here can be obtained from conventional metrics.1 aHitzler, Pascal1 aSeda, Anthony1 aSeda, Anthony, K. uhttp://www.knoesis.org/node/192801259nas a2200133 4500008004100000245006200041210005900103260002600162300001200188520084600200100002201046700002001068856003701088 2000 eng d00aA New Fixed-point Theorem for Logic Programming Semantics0 aNew Fixedpoint Theorem for Logic Programming Semantics aOrlando, Florida, USA a418-4233 aWe present a new fixed-point theorem akin to the Banach contraction mapping theorem, but in the context of a novel notion of generalized metric space, and show how it can be applied to analyse the denotational semantics of certain logic programs. The theorem is obtained by generalizing a theorem of Priess-Crampe and Ribenboim, which grew out of applications within valuation theory, but is also inspired by a theorem of S.G. Matthews which grew out of applications to conventional programming language semantics. The class of programs to which we apply our theorem was defined previously by us in terms of operators using three-valued logics. However, the new treatment we provide here is short and intuitive, and provides further evidence that metriclike structures are an appropriate setting for the study of logic programming semantics.1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/118600296nas a2200097 4500008004100000245004000041210003800081100002200119700002000141856003700161 2000 eng d00aA Topological View of Acceptability0 aTopological View of Acceptability1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/192901283nas a2200133 4500008004100000245003400041210003400075260011700109520076200226653008200988100002201070700002001092856003701112 1999 eng d00aAcceptable Programs Revisited0 aAcceptable Programs Revisited bWorkshop on Verification in Logic Programming, 16th International Conference on Logic Programming (ICLP'99),3 aAcceptable logic programs have been studied extensively in the context of proving termination of Prolog programs. It is difficult, however, to establish acceptability from the definition since this depends on finding a suitable model, which need not be a Herbrand model in general, together with a suitable level mapping that one can use to check the conditions which characterize acceptability. In this paper, we will see that when working over a fixed but arbitrary preinterpretation, a method can be provided for obtaining both a suitable model and a canonical level mapping which are sufficient for this purpose. Furthermore, the canonical model and level mapping obtained will turn out to be sufficient for discussing termination of non-ground queries.10al and o and g and i and c and and p and r and o and g and r and a and m and s1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/179900296nas a2200097 4500008004100000245004000041210003800081100002200119700002000141856003700161 1999 eng d00aA Characterization of Acceptability0 aCharacterization of Acceptability1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/118301054nas a2200109 4500008004100000245007100041210006900112520068400181100002200865700002000887856003700907 1999 eng d00aCharacterizations of Classes of Programs by Three-valued Operators0 aCharacterizations of Classes of Programs by Threevalued Operator3 aSeveral important classes of normal logic programs, including the classes of acyclic, acceptable, and locally hierarchical programs, have the property that every program in the class has a unique twovalued supported model. In this paper, we call such classes unique supported model classes. We analyse and characterize these classes by means of operators on three-valued logics. Our studies will motivate the definition of a larger unique supported model class which we call the class of Phi-accessible programs. Finally, we show that the class of Phi -accessible programs is computationally adequate in that every partial recursive function can be implemented by such a program.1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/118401809nas a2200121 4500008004100000245007300041210006900114260006400183520136100247100002201608700002001630856003701650 1999 eng d00aMultivalued Mappings, Fixed-Point Theorems and Disjunctive Databases0 aMultivalued Mappings FixedPoint Theorems and Disjunctive Databas bElectronic Workshops in Computing, British Computer Society3 aIn this paper, we discuss the semantics of disjunctive programs and databases and show how multivalued mappings and their fixed points arise naturally within this context. A number of fixed-point theorems for multivalued mappings are considered, some of which are already known and some of which are new. The notion of a normal derivative of a disjunctive program is introduced. Normal derivatives are normal logic programs which are determined by the disjunctive program. Thus, the well-known single-step operator associated with a normal derivative is single-valued, and its fixed points can be found by well-established means. It is shown how fixed points of the multivalued mapping determined by a disjunctive program relate to the fixed points of the single-step operators coming from its normal derivatives. This procedure has potential for simplifying the construction of models of disjunctive databases, and this point is discussed. Most of the results for multivalued mappings rest on corresponding, known results concerning fixed points of single-valued mappings. Since the latter results are frequently referred to, they have been collected together for convenience in a survey which should be of independent interest as well as being preparatory for the later results. Finally, a number of problems and issues raised by this work are discussed.1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/180201403nas a2200157 4500008004100000245013100041210006900172300001200241520083200253653001701085653003901102653002501141100002201166700002001188856003701208 1999 eng d00aSome Issues Concerning Fixed-Points in Computational Logic: Quasi-Metrics, Multivalued Mappings and the Knaster-Tarski Theorem0 aSome Issues Concerning FixedPoints in Computational Logic QuasiM a223-2503 aMany questions concerning the semantics of disjunctive databases and of logic programming systems depend on the fixed points of various multivalued mappings and operations determined by the database or program. We discuss known versions for multivalued mappings of the Knaster-Tarski theorem and of the Banach contraction mapping theorem and formulate a version of the classical fixed point theorem (sometimes attributed to Kleene) which is new. All these results have applications to the semantics of disjunctive logic programs, and we will describe a class of programs to which the new theorem can be applied. We also show that a unification of the latter two theorems is possible, using quasi-metrics, which parallels the well-known unification of Rutten and Smyth in the case of conventional programming language semantics.10afixed points10aKnaster Tarski and Kleene theorems10amultivalued mappings1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/162901162nas a2200121 4500008004100000245004500041210004400086260004800130520078300178100002200961700002000983856003701003 1998 eng d00aStrictly Level-Decreasing Logic Programs0 aStrictly LevelDecreasing Logic Programs bthe Second Irish Workshop on Formal Methods3 aWe study strictly level-decreasing logic programs (sld-programs) as defined earlier by the present authors. It will be seen that sld-programs, unlike most other classes of logic programs, have both a highly intuitive declarative semantics, given as a unique supported model, and are computationally adequate in the sense that every partial recursive function can be represented by some sld-program *P*. Allowing for a safe use of cuts, an interpreter based on SLDNF-resolution, as implemented for example in standard Prolog systems, is shown to be sound and complete with respect to this class of programs. Furthermore, we study connections between topological dynamics and logic programming which are suggested by our approach to the declarative semantics of sld-programs.1 aSeda, Anthony, K.1 aHitzler, Pascal uhttp://www.knoesis.org/node/180100278nas a2200085 4500008004100000245004700041210004700088100002000135856003700155 1997 eng d00aDer Kontraktionssatz auf metrischen Raumen0 aDer Kontraktionssatz auf metrischen Raumen1 aHitzler, Pascal uhttp://www.knoesis.org/node/204000281nas a2200109 4500008004100000245002100041210002100062100001400083700001700097700002000114856003700134 1997 eng d00aFixpunktsemantik0 aFixpunktsemantik1 aGrimm, M.1 aKalmbach, G.1 aHitzler, Pascal uhttp://www.knoesis.org/node/203900329nas a2200097 4500008004100000245005900041210005600100100001800156700002000174856003700194 1997 eng d00aSur les programmes logiques localement stratifiés0 aSur les programmes logiques localement stratifi233s1 aSeda, Anthony1 aHitzler, Pascal uhttp://www.knoesis.org/node/192700256nas a2200097 4500008004100000245001700041210001700058100002600075700002000101856003700121 1996 eng d00aSpieltheorie0 aSpieltheorie1 aChocholaty, Alexander1 aHitzler, Pascal uhttp://www.knoesis.org/node/2042